SILENCES IN MUSIC ARE MUSICAL NOT SILENT: AN EXPLORATORY STUDY OF CONTEXT EFFECTS ON THE EXPERIENCE OF M USICAL PAUSES

ELIZABETH H ELLMUTH M ARGULIS University of Arknusns

SILENCES IN MUSIC ARE DISTINGUISHED aCOUStically along only one dimension: the length of time they occupy. However, like pauses in speech, they are distin -guished syntactically along many dimensions, depend-ing on the context in which they occu r. In two experiments, one using musical excerpts from commer-cially available recordings, and the other using simpler constructed excerpts, participants' reactions to silences were assessed. Paticiponts pressed a button when they heard a period of silence begin and end, moved a slider to indicate perceived changes in musical tension across the course of each excerpt, and answered a series of questions about each silence, including questions about its duration, placement, sa lience, and metric qualities. Musical context, especially tonal context, affected the response to silence as measured by all three tasks. Specifically, silences following tonal closure were identi-fied more quickly and perceived as less tense than silences following music lacking such closure.

Received December 16, 2005, nccepted Februnry 7, 2007. Key words: pauses, silence, syntax, tension, tonality

MUSIC ENGAGES LISTENERS IN complex and myriad ways. The acoustic signal does not transform transparently into heard experi-ence; rather, the acoustic signal meets and partners with perceptual principles, listening histories, and perhaps a "musical grammar" (Jackendoff & Lerdahl, 2006) to produce an experience that engages the body (Janata & Grafton, 2003; Urista, 2003), the intellect (Webster & Rodriguez, 1997), and the emotions (Juslin & Sloboda, 2003). Much research has explored the ways that con-text can transform the experience of an individual acoustic element. For example, a tone of a particular pitch, loudness, and duration can be experienced as accented in one (metric) context and unaccented in another (Parncutt, 1994). Similarly, a tone of a particu-lar pitch, loudness, and duration can be experienced as

stable and conclusive in one (tonal) context, and unsta-ble and implicative in another (Krumhansl, 1990). Yet little research has addressed the ways in which context mediates the experience of perhaps the most obviously context-dependent acoustic element: silence.

Acoustically, silences can be defined as periods during which the acoustic signal descends below some thresh-old of detectable volume. Acoust.ic silences are com-putable automatically by a program designed to analyze sound signals and extract spans during which the signal falls below the criterio n level. In this study, the criterion level was double the lowest ampl itude in the excerpt. The moment the excerpt fell below that cutoff was con-sidered to be the silence onset, and the moment it went back above it was considered to be the silence offset. The duration of the acoustic silence was the time from onset to offset, as determined by t!he criterion.

Acoustic silences can be thought -of as one-dimensional gaps consisting purely of duration; the duration from the end of the previous sound to the start -of the next. Yet silences are experienced as anything but one-dimen-sional; in fact, musicians often speak of silences as par-ticularly important loci of expressivity.1 Perceived silences depend inextricably on musical context. The same acoustic silence, embedded in two different excerpts, can be perceived dramatically differently. Impressions of the music that preceded the silenc,e seep into the gap, as do expecta tions about what may follow. These impres-sions and expecta tions can cause two identical acoustic silences to seem like they occupy different lengths of time, or ca rry different amounts of musical tension, or function differently in other ways. This paper explores the transformation from acoustic to perceived silence.2 What aspects of the surrounding contex1 impinge upon the silent period and make it seem to actually so11nd dif-ferent? Reaction times, tension slider movements, and

1An abundance o f well known quotations address the expressive importonce of .nus ical silence. One exa.rnple, from pi:mist Artur Schnabel: "The notes I handle no better than many pianists. But the pauses between the notes- ah, that is where the art resides.''

2Nakajima ( 1987) rnokcs a s imiku dis tinctio n between physical and subjective pauses, and Zell ner ( I994) h

486 E. H. MMgulis

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question responses were used to gauge the nature of the perceived silence that listeners constructed out of the combination of the acoustic silence and the surrounding context.

Consider Figure I, an excerpt from Schubert's Moment Musicaux Op 94, No 4, and Figure 2, an adapted version of the same excerpt. In the original version (Figure I), the silence interrupts the expected resolution to a downbeat cadence o n a tonic C-sharp minor chord. In the adapted version ( Figure 2), the silence follows cadentia l resolution on a downbeat C-sharp minor chord. Acoustically, the silences differ only in length (and perhaps not even that, if a performer chose to sus-tain both silences for the same duration, invoking the freedom permitted by the fermata). Perceptually, how-ever, the silences differ markedly. The silence in Figure I, by virtue of occurring in place of an expected continu-ation, draws attention to itself. The silence in Figure 2 is inconspicuous, falling at a grouping boundary after cad entia! closure. The silence in Figure I seems marked at its onset, but the silence in Figure 2 emerges subtly out of the decay of the preceding chord. The silence in Figure I, following an open gesture, seems tense and forward-leaning, but the silence in Figure 2, following a closed one, seems relaxed and at rest. (Indeed, the e> .. pectant tension permeating the silence in Figure I makes the subsequent tu rn to the major modality more effective).

Context, in short, can transform the same acoustic silence into very different perceived silences.

London ( 1993) explores the anticipatory metric mechanisms that can make a rest (an acoustic silence) sound loud (a perceived quality) . He quotes Cooper and Meyer's ( 1960) observation that the downbeat of measure 280 in the first movement of Beethoven's Eroicn Symphony is "the lo udest silence in musica l liter-ature" (p. 139), occurring at the mo ment of a projected downbeat on the largest scale. As London describes it, "a t the very moment where we expect the culmination of a tissue of musical processes, all we get is the 'default' articu lation of the downbeat as we count along. With so much riding on that moment, the little metric "click" we hear/create in our heads is deafeningly loud indeed" (p. 2). Meter is perhaps the most explo red of the musi-cal phenomena that can transform acoustic silences into musically significant perceived silences, but other parameters such as form and tonal structUle can have similar effects.

Kraemer, Macrae, Green and Kelley (2005) used func-tional magnetic resonance imaging to scan participants while they listened to fami liar and unfamiliar pieces of music, where short sections (2-5 s) were replaced by silent gaps. Participants showed more activation in the auditory association areas during silent gaps in familiar pieces than during gaps in unfamiliar pieces; in other

manueltizondiazHighlighthttp://www.dartmouth.edu/~bil/pubs/kraemer_2005_nature.pdf

Silcmcts ;, Musir 487

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words, b rain activity during otherwise identical acoustic silences differed depending on the context in which the silence was embedded. "Simply muting short gaps of familiar music was sufficient to trigger auditory imagery-a finding that indicates the obligatory nature of this phenomenon. Corroborating this observation, all subjects reported subject ively hear ing a continuation of the fami liar songs, but not of the unfamiliar songs, during the gaps in the music" (p. 158). Conlext can transform an acoust ic silence into a perceived si lence that is fil led with imagined music.

The complex time course of musical processing means that silences are invariably imbued wi th the lin-gering perception of past events as well as the anticipa-tion of future ones. Tekman and Bharucha (1998) showed that for chords, priming effects (the facilitation of processing for chords that are typical consequents, and the enhancement of their perceived consonance) persist through si lent periods of as long as 2,450 ms. These priming effects are t riggered and persist even when the prime is as short as 50 ms, suggesting a qu ick rise and slow decay for priming effects across silences. Kallman and Massaro (1979, 1983) likewise illustrates that although the presentation of an intervening audi-tory stimulus significantly decreases recogn ition mem-ory, silent retention intervals only slightly decrease recognition memory for tones. Dureau (2005) recorded

infants' heart rate and behavior th rough alternating periods of music and silence. She found that the arousal from the initial auditory stimulus lasted through the subsequent silent period, preventing the measures from returning to baseline. These results speak to the degree to which the preceding musical context can influence the experience of empty periods.

Pauses serve 10 segment all kinds of sequentia l mate-ria l (Restle, I 972), including language, where the length of the pause correla1cs with the hierarchica l level of the segment end ing (Goldman-Eisler, 1972). Linguists, in fact, make a distinction between physicnl pauses and perceived pauses (Zellner, 1994)-a distinction which is approximately equivalent to the distinction made in this study between acoustic and perceived silences, where perceived pauses are dependent on linguistic context. In speech, pauses tend to be long and frequent between words that don't group together, and short and less fre-quent between words that are interdependent (Grosjean, Grosjean, & Lane 1979). Mean durations of s ilent pauses in speech are comparable to the durations of the musical pauses used in this study; in an interview, mean pauses by speakers were 520 ms, in describing a cartoon (a relatively more complex task), mean pauses were 1320 ms (Grosjean & Deschamps, 1975).

Deutsch (1980) showed that pauses segment melodies, determining which melodic groups get remembered as

chunks. According to Lerdahl and Jackendoff ( 1983), it is interonset interval, rather than si lence per se, that contributes to the determination of group boundaries. One of the theory's grouping preference rules (Slur/Rest) advocates locating a boundary at spots where the time from the end of one note to the start of the next is longer than the value of surrounding end-to-start spaces, but another (Attack-point) advocates locating a boundary at spots where the time from the start of one note to the start of the next is longer than surrounding start-to-start durations. The Attack-point rule does not distinguish between held notes (where a note is sustained from one attack-point to the next) and pauses (where a rest follows the attack point of the first note). In an empirical test of grouping strategies, Fran-kland and Cohen (2004) found that the Attack-point rule accounted for boundary placement better than any of the other rules tested, and that the Slur/Rest rule was only invoked by participants in response to one of the stimulus melodies. These data suggest that under some circumstances, silences and sustained notes can func-tion in syntactically similar ways. Sloboda and Gregory (1980) distinguished between physical markers for phrase boundaries, such as a note of relatively long duration or a relatively long pause, and structural markers for phrase boundaries, such as cadences (stan-dardized harmonic progressions that often occur at phrase ends). T he study examined click migration, the tendency for clicks to be misremembered as occurring closer to phrase bow1daries than they occurred in real-ity, a phenomenon that characterizes both music and language. Click migration shows that structural cues are sufficient to create anticipation for phrase boundaries, and suggests that the psychological endpoint of phrases may be at the beginning of the final, elongated, closural pitch, rather than at the pitch's end. If th is is the case, the psychological difference between a short final note fol-lowed by a silence and a final note held for the length of the silence may be negligible.

The present study uses estimated duration as one measure of contextual effects on silence. There is a large literature on time estimation in psychology, ranging from studies on the "watched-pot phenomenon" (Block, George, & Reed, 1980; Cahoon & Edmonds, 1980)- the overestimation of time periods in which the estimator is expectantly waiting for something to happen-to studies on "turn-taking" in spoken language-the extraction of temporal regularities in speech that allow people in ordinary conversation to neither interrupt nor enter too late after their partner's utterance (Jaffe & Feldstein, 1972). Block and Zakay ( 1997) review the time estimation li terature. Theories of time estimation

have been put forth by Fraissc ( 1984), who suggested that expectancies increase experienced duration by drawing attention to the passage of time, and by Orn-stein ( 1969), who suggested that expectancies increase experienced duration by encouraging the perceiver to attend more closely to the environment, increasing the amount of information encoded into memory, and thus inflating the amount of time that seems to have passed.

Jones and Boltz (1989) outline a framework for understanding how structure guides different modes of attending that yield different time estimation strategies. According to this framework, if the end of an event comes later than expected, the event will seem long and its duration will be overestimated; whereas if the end of an event comes earlier than expected, the event will seem short and its d uration will be underestimated. However, if the structure of the stimulus does not afford the for-mation of clear temporal expectancies, duration estima-tion will be based on the number of changes or segments within the event, as described by Ornstein ( 1969).

Boltz (1989) asked participants to compare the dura-tions of folk songs ending with different degrees of tonal resolution. Melodies ending on the leading tone (thus lacking tonal resolution) were judged to be shorter than those ending on the tonic (thus possessing tonal resolution). Boltz hypothesized that the expecta-tion for an impending tonic made the leading tone end-ings seem too early, causing the tune duration to be underestimated. In Jones, Boltz, and Klein (1993 ), par-ticipants heard melodies with a phrase structure of high temporal regularity, and were asked to judge the melody length. In some melodies, the final phrase was extended or contracted so that the final note occurred too early or too late in comparison to the previously established phrase regu larities. When the final note occurred too early, participants underestimated the melody's dura-tion, and when it occurred too late, participants overes-timated the duration.

In Boltz ( 1991 ), participants over or underestimated durations for the same stimulus, depending on the coherence of the level of structure attended to (either the temporally p redictable higher level phrase structure or the temporally predictable lower level contour changes among adjacent notes). Participants attending to the phrase structure over or underestimated the stimulus duration based on the expected endpoin t, but participants attending to the contour over or underes-timated the duration based on the number of contour changes (where more changes yielded longer estima-tions). In Boltz (1993), participants judged the dura-tion of a music perception task, and the duration of a

waiting period within an experiment. They used the same strategies to under or overestimate durations as the participants in the music studies. These findings provide strong support for a general, domain inde-pendent relationship between expectancy and time esti-mation. However, they concern the estimation of relatively long periods: on the order of several seconds o r more. The si lences used in the present study are much shorter, falling well within the range of the per-ceptual present. The estimation of such short durations might rely on different cognitive processes than the esti-mation of longer ones. Nakajima (1987) investigated the estimation of shorter durations, specifically empty durations between 40 and 600 ms, marked on either end by short sound bursts. He found that the estimated duration of periods within this range were proportional to the physical duration plus a constant of -80 ms. His model distinguishes between physical duration, the measured time between the two sound bursts, and sub-jective duration, the perceived time between the two. This distinction parallels the distinction made in this paper between acoustic and perceived silences.

Mattys, Pleydell-Pearce, Melhorn, and Whitecross (2005) also worked with short silences and found that detection latencies for 200 ms pauses inserted into the last word of spoken sentences depended on the lexical-semantic context of the preceding sentence. Similarly, reactions to pauses in music are likely to depend on the surrounding context. Silences in music occur norma-tively at ph1ase boundaries (Deliege, 1987; Huron, 2006; Lerdahl & )ackendoff, 1983; Temperley, 2001; Wertheimer, 1923/ 1938), where they contribute to a gestalt separation that spl its the music into two chunks: one presi lence, and one post. David Huron (personal communicat ion, December 30, 2006) used the software toolkit Humdrum (Huron, 1995) to perform an analy-sis of an often-used corpus of Western music: Helmut Schaffrath's Essen Folksong Collection (1995) . In the collection's 687 German ballads, there are 27,664 notes and 1,192 rests in 3,088 explicitly marked phrases. Of the rests, 1,130 (95%) occur at the ends of phrases, and only 62 (5%) occur within phrases.

Silences in music most often follow closure. Indeed, as in speech, where the length of the pause correlates with the hierarchic level of the structure achieving do-sure, longer silences in music tend to follow instances of tonal closure on a larger scale (e.g., the final cadence of a section versus the final cadence of a phrase, Berry, 1985). Yet silences can also occur midphrase for expres-sive effect, at points of dramatic tension or interruption, before tonal closure has been achieved. This study hypothesizes that listeners will perceive silence differently

Silct~cts ;, Musir 489

when it follows closed and open musical gestures; specif-ically, that listeners will: (I) iden tity a silence more quickly when it follows a closed gesture; (2) perceive more tension in silence following an open gesture: and (3) respond systematically differently to direct questions about silence when it follows open and closed segments.

In Experiment I, participants were played excerpts from commercial recordings that contained an instance of musical silence. They were asked to perform three tasks in relation to the excerpts (with one task per stim-ulus presentation). Pint, they were asked to indicate when the silent periods started and ended. Second, they were asked to move a slider to indicate their perception of fluctuations in tension across the course of the excerpt (cf. Frederickson, 1995; Schubert, 2004; Vines, Krumhansl, Wanderley, & Levitin, 2006). Third, they were asked to answer a series of questions regarding their experience of the silence and the excerpt. In Experiment 2, participants were asked to perform the same tasks in relation to constructed musical excerpts that were isochronous (except for two excerpts featur-ing an accelerando and two featuring a ritardando), monophonic, and unitimbral. Experiment I provided a more ecologically valid study, in which listeners were likely to respond more closely to the way they would in non laborato ry listening, but Experiment 2 provided a controlled study, in which certain musical parameters were held constant and others varied to permit the iso-lation of the impact of factors theorized to influence the resu lts for Experiment I. Participants without musical training were selected for both experiments, so that responses to the silences would reflect reactions to music, rather than assessments based on prior training.

Experiment 1

Metl1od

PARTICIPANTS Twenty-five participants were recruited from "Intro-duction to Music;' a class at Northwestern University with no prerequisites, intended for non-music majors. The goal was to recruit participants without substantial training in music. As compensation par ticipants were given extra credit in the class and $5. The study took about one hour to complete.

Eight out of the 25 participants (32%) reported no musical training whatsoever. Another nine (36o/o) repor-ted five or fewer years of instrumental lessons. Seven (28o/o) reported between six and ten years of instru-mental lessons, and the remaining participant reported 13 years of lessons. Five of the participants (20o/o) reported some training in music theory, but all except

490 E. H. Mt~rg11l11

one of these five reported that the training was rudi-mentary and lasted one year or less. None of the partic-ipants characterized themselves as musicians, and none were music majors.

The participants reported listening to music between I and 34 hours per week (M = II; SD = 10), and attend-ing between 0 and 20 concerts a year (M = 3; SD = 4). No participant data was summarily excluded. MATERIALS

Stimuli consisted of 20 musical excerpts taken from commercial recordings of tonal repertoire by composers from Bach to Mussorgsky, featuring ensembles ranging from solo piano to full orchestra (see Appendix A). No vocal music was included, to avoid the complicating factor of text (one excerpt came from a choral work, but the excerpt itself was entirely instrumental). Each excerpt featured a period of silence. This silence occurred naturally on the recording and was not artifi-cially introduced. The intent of the stimuli collection was to sample as wide a variety of musical contexts for these silences as possible. The excerpts ranged in length from 5.9 to 23.5 s (M = 14.1,SD= 4.7). The silences fea-tured in the excerpts ranged in length from 0.5 to 3.7 s (M = 1.3, SD = 0.8). The length of the silences did not correlate with the tempo of the excerpts; i.e., long silences were found in both fast and slow excerpts, as were short silences. Excerpt and silence timings were established with a short program written in MATLAB. This program scanned the excerpts for the lowest ampli-tude, and then marked the silence onset as the moment the ampl itude descended below the criterion level of twice the lowest amplitude, and the silence offset as the moment the amplitude returned to the criterion level.

The recordings were presented over ALES IS point 7 speakers with a shielded reference monitor, 4 ohms impedance in n Wenger V-Ready Anachoic Chamber. The questions wcoe presented and responses wcoc col-lected in MediaLab (Stages 2 and 3) and Direct RT (Stage I) (Jarvis, 2004) on an IBM Thinkpad T23 running Windows 2000 Professional. DirectRT per-mits a timing resolution of l ms, and the latency due to the mouse did not change from excerp t to excerpt, making precise timing comparisons possible. Tension slider responses were collected with a Logitech Extreme 3D Pro joystick moving in 1 dimension (for-ward to back). PROCEDURE

Participants began the experiment by responding to a questionnaire about their mJsical background.

ln Stage I of the study, following an instruction set, participants heard a series of musical excerpts and for

each clicked the appropriate onscrcen box to indicate when they heard periods of silence begin and end. Since reaction time was the measure of interest, it was impor-tant that participants respond qu ickly. Although each excerpt contained only one si lence, multiple boxes were included to prevent participants from indulging in the extra calculation time that might be necessary to decide whether what seemed like the sta rt of a silence was rea ll y the star t of the main silence in the excerpt; in other words, including multiple boxes permitted them to register false alarms. After the presentation of each excerpt, to further encourage fast responding, onscreen te.u reminded participants to be sure to "respond as quickly and accurately as possible." Par-ticipants were given two pract ice excerpts. After the practice trials, the)' heard the 20 musical excerpts in random order, then the same 20 excerpts in a different random order.

Participants were asked to take a short break and were then presented with Stage 2 or Stage 3 of the study (the order of these stages was randomized). In Stage 2, par-ticipants heard a series of musical excerpts and were asked "to move a joystick to indicate the changes in ten-sion [they) perceive[d) across the course of musical excerpts." Participants were not informed that the excerpts would be the same as those heard in Stage l. Participants moved the joystick forward to indicate increasing tension and back to indicate decreasing ten-sion. They were encouraged to use the full range of the joystick. They were given two practice trials and then performed the task for each of the 20 excerpts.

In Stage 3, participants responded to a series of ques-tions about the musical excerpts. Again, they were not informed that these would be the same excerpts used in Stages I and 2. (In poststudy discussion with the exper-imenter, many participants reported being unaware that they had heard any excerpt in more than one stage.) Participants heard each of the 20 musical excerpts fol-lowed by the different questions in random order. Halfway through the questions, they heard the excerpt a second time. Participants responded using the key-board. The questions consisted of the following:

Did you hear a period of silence during the excerpt? (Participants selected yes or no)

About how many seconds did the EXCERPT last? (Participants entered a number)

About how many seconds did the SILENCE last? (Participants entered a number)

Where was the silence located within the excerpt? (Participants indicated a rating on a 7-point scale from "at the start" to "at the end")

Did you experience a sensation of beats (or imag-ined head nods, or hand claps) during the silence? (Participants selected yes or no)

How unnoticeable or noticeable was your experi-ence of beats during the silence? (Participants indi-cated a rating on a 7-point scale from "very unnotice-able" to "very noticeable")

Estimate the number of beats you imagined during the silence (Pa rticipants entered a number}

How expected or surprising was the SILENCE itself? (Participants indicated a rating on a 7 -point scale from "very expected" to "very surprising")

How expected or surprising was the music that immediately FOLLOWED the period of silence? (Participants indicated a rating on a 7-point scale from "very expected" to "very surprising")

How badly or well did the silence fit within the con-text of the excerpt? (Participants indicated a rating on a 7 -point scale from "very badly" to "very well"}

How unnoticeable or noticeable was the silence? (Participants indicated a rating on a 7-point scale from "very unnoticeable" to "very noticeable")

How relaxed or tense did the silence seem? (Partic-ipants indicated a rating on a 7-point scale from "very relaxed" to "very tense")

Silcmct'1 ;, Musir 491

Results nnd Diswssion RTS (STAGE I) Boxplots were produced for the reaction times to the silence onset and offset in each excerpt, and extreme cases (extremely early or late responses prc>Sumed to be due to participant error) were removed. Boxplot edges were Tukey's hinges and extreme cases were identified as values more than three interquartile ranges from the edge of a box. Using these criteria, an average of 2 out of the 25 responses to each silence onset were discarded for each excerpt. Since the order of presentation (first or second hearing) d id not affect reaction t imes to silent onsets or offsets, F(l, 19) = 1.01, p = .46, reaction times from both presentations were pooled and included. Across all excerpts, the mean reaction time to silence onsets was 148 ms (SD = 458 ms). The mean reaction time to silence offsets was 421 ms (SD = 413 ms). Stan-dard deviations were large because there was little consis-tency from excerpt to excerpt in terms of orchestration, dynamics, phrase structure, or tempo, leaving much unpredictability in the stimuli. Additionally, participants often responded early to silence onsets when the preced-ing event was sustained and faded gradually(see Table I ). (Experiment 2 featured sharp note releases and more predictability from excerpt to excerpt, significantly

TABLE 1. Mean reaction times and standard error to silence onsets for excerpts in Experiment 1.

Excerpt

I. Bach St. Mauhcw Passion No. 36 2. Beethoven Op. I 0 No. 3, M'~ I, Excerpt 2 3. Beethoven String Q uartet Op. 131, Presto, Excerpt 2 4. Beethoven String Quartet Op. 131, Presto, Excerpt I 5. Beethoven Piano Sonata Op. 10 No.3, Mvt. I , Excerpt 2 6. Chopin Nocturne Op. 32 No. I 7. Chopin Nocturne Op. 62 No. I 8. Mussorgsky Pictures at an Exhibition (Ravel orchestration) 1\o. 7 The Market 9. Beethoven Piano Sonata Op. 126, M'1. I

I 0. Haydn Symphony No. I 04, Minuet II . Haydn String Quartet Op. I 03, Mvt. I, Excerpt I 12. Haydn String Quartet Op. 77 No. I, Mvt. 2 13. Haydn String Quartet Op. 103, Mvt. I, Excerpt 2 14. Mozart Fantasy inC Minor, Excerpt I I 5. Mozart Fantasy in C Minor, Excerpt 2 16. Mussorgsky Pictures at an Exhibition (Ravel orchestration)

No. I 0 The Great Gate of Kiev 17. Schubert Moment Musicaux Op. 94 No. 4 18. Schubert Moment Muiscaux Op. 94 No. 2 19. Tchaikovsky Symphony No.4, Mvt. I 20. Wagner Prelude to Tristan and Isolde

Mean RT to Standard Silence Onset (ms) Error

233 69 422 67

- 184 71 552 65 617 67 86 66

- 696 65 35 65 96 66

449 72 -693 66

300 66 435 65 -69 65 748 72 171 69

333 67 - 195 65

49 65 693 71

4 92 11. II. Mnrguli1

reducing the standard deviations for the reaction times, see discussion below).

To assess the effect of preceding context on the speed with which silences were recognized as such, an A NOVA was performed with onset reactio n times as the dependent variable, and pieces (20) and subjects (25) as variables. Reaction times varied significantly across pieces, F( 19, 452) = 13.99, p < .001. A p riori post-hoc contrasts were performed to assess the specific effects of tonal, metric, and rhythmic context on onset reaction times.

If the part of the excerpt immediately preceding the silence ended with a tonic chord, reaction times were significantly faster than othenvise, F( I, 483) = 7.82, p < .01. Contrastingly, if the part of the excerpt immedi-ately preceding the silence ended with a predominant chord, reaction times were s ignificantly slower than o therwise, F( I, 483) = 7.25, p < .01. These results are consistent with the hypothesis that untrained listeners react quickly when silence follows a closura l harmony (to nic), but slowly when silence follows a n implicative harmony (predominant). Participants' responses to tonal fea tures retlected their responses not to har-monies in isolation, but to hannonies as they are typi-cally embedded within ph rase structures; tonic harmonies are much more typical of phrase endings than predominant harmonies.

When the prevailing metric framework convinces a listener to expect strong metric accent at a particular time point, it is particularly surprising if no note attack occurs there ( Lcrdalll & jackendoff, 1983). In other words, it is more likely that a note attack wil l occur ot a metric downbeat than at an upbeat, and thus less likely that 11 si le nce will begin o n a metric downbeat than on on upbeat. If the silence started on a me tric downbcut, reaction t imes were significantly slower than otherwise, F( I, 483} = 22.87,p < .00 1. Presumably, listeners' expec-tation for a note attack on the downbeat delayed their response to the silence that occurred instead. This result is consistent with the hypothesis that metric structure shapes silence perception.

Rhythmically, long notes contribute to the creation of closure, and are more normatively followed by silences than are short notes (Lerdahl & Jackendoff, 1983). If the silence followed a long note (defined as a note at least four times longer than the average du rat ion of the pre-ceding notes), reactio n t imes to silence o nsets were sig-nifican tly faster than otherwise, F(l, 483) = 43. 15, p < .001. Long notes are representative of durational clo-sure (Narmour, 1990), and are more likely to end a phrase than short notes. Closure, whether tonal or durational, speeded silence identification.

TENSION (STAGE 2l Stage 2 of the experiment assessed participants' experi-ence of musical tension during the silent periods. Par-ticipants moved a joystick forward and back while each excerpt progressed to indicate iJlCreasing and decreas-ing tensio n. Since silences in this experiment lasted for different lengths of time, but no silence lasted for less than 500 ms, to facilitate comparison the quantitative analysis examined only the joystick movements d uring the first 500 ms of each silence.

To assess the consistency wi th which participants applied the concept of tension, results from Stage 2 were compared with results from Stage 3. As o ne part of Stage 3, participants were asked after the completion of each excerpt to estimate how tense the silence had seemed on a scale from I to 7, where I signified "extremely relaxed" and 7 "extremely tense." Correla-tions between the average joystick posit io n in Stage 2 d uring the first 500 ms of each excerpt's silence and the rating of the silence's tension in Stage 3 were high, r(l9) = . 75, p < .001. The high correlations between real time assessments of tension via the joystick in Stage 2 and post excerpt assessments of tension via the ratings in Stage 3 suggest that participants were consistent about the way they applied the concept of tension; that the responses during the first 500 ms of the silence were rep-resentative of the overall impression of the silence (or that the qualities of the silence's beginning were more salient in retrospect), and that participants were paying attention in both stages of the experiment.

An ANOVA was performed with the mean joystick positions during the first 500 ms of each silence as the dependent variable, and pieces (20) and subjects (25) as

fi~et ors (see Table 2}. Mean joystick positio ns (repre-senting tension levels) va ried signil1can tly ac ross pieces, F( I, 19) = 282.63, p < .00 I. A priori post-noc contrasts were performed to assess the effect of harmonic con-text.lf a tonic chord preceded the silence, the silent period was perceived as less tense than othenvise, F(l, 24) = 10.27, p < .005. On the other hand, if a predominant chord preceded the silence, the silent period was per-ceived as more tense than otherwise, F( l, 24) = 13.18, p < .00 I. These results suggest that the harm onic ten-sion of the preceding chord carried over strongly into the ensuing silence.

The preceding analysis compared respo nses during tile fi rst 500 ms of each si lence, but a visua l inspection of the shape of tension responses across the course of entire silences yielded an additional interesting obser-vation. As an example of the differences in perceptions of tension during the silences in the different excerpts, compare the mean slider positions across the entire

Silct~cts ;., Musir 493

TABLE 2. Mean tension ratings and standard error to first 500 ms of silences for excerpts in Experiment I.

Mean Tension Rating for Standard Excerpt first 500 ms of Silence Error

I. Bach St. Matthew Passion No. 36 73 20 2. Beethoven Op. 10 No.3, Mvt. I, Excerpt 2 65 14 3. Beethoven String Quartet Op. 131, Presto, Excerpt 2 60 16 4. Beethoven String Quartet Op. 131, Presto, Excerpt I 57 13 5. Beethoven Piano Sonata Qp. I 0 No. 3, Mvt. I, Excerpt 2 60 13 6. Chopin Nocturne Op. 32 No. I 58 12 7. Chopin Nocturne Op. 62 No. I 64 16 8. Mussorgsky Pictures at an Exhibition (Ravel orche.stration) No.7 The Market 80 24 9. Beethoven Piano Sonata Op. 126, Mvt. I

I 0. Haydn Symphony No. I 04, Minuet II . Haydn String Quartet Op. 103, Mvt. I, Excerpt I 12. Haydn String Quartet Op. 77 No. I, Mvt. 2 13. Haydn String Quartet Op. 103, M,t. I, Excerpt 2 14. Mozart Fantasy inC Minor, Excerpt I 15. Mozart Fantasy in C Minor, Excerpt 2 16. Mussorgsb.-y Pictures at an Exhibition (Ravel orchestration)

No. I 0 The Great Gate of Kiev 17. Schubert Moment Musicaux Op. 94 No.4 18. Schubert Moment Muiscaux Op. 94 No. 2 19. TchaikovsJ..;' Symphony No.4, M\1. I 20. Wagner Prelude to Tristan and Isolde

silence in two excerpts from Haydn String Quartets: an unclosed excerpt from Op. 77, No. 1 (with a silence of 1400 ms ), and a closed excerpt from Op. 103 (with a

80

60

50

100 2()0 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

Milliseconds from Start of Silence

FIGURE 3. Mean tension slider positions for all participants during the silence in an excerpt from a Haydn String Quartet (Op. 77, No. 1, Move ment 2, measure 29). A predominant chord (no tonal closure) precedes this silence.

78 16 80 IS 61 14 53 5 8 1 19 65 19 87 17 80 20

67 16 82 18 56 12 59 14

silence o f 1700 m s). These excerpts are particularly use-ful for comparison, because they contrast presilence closure and openne.ss in excerpts from the same genre by the same composer with comparable silence lengths. Figure 3 and 4 present mean tension responses, aver-aged across all participants, for the entire course of each silence. Figure 3 shows that the tension from the inter-rupted predominant chord suffuses most of the silence in Op. 77, No. I, with no significant decrease perceived until after a full 1000 ms of si lence. Contrastingly, Figure 4 shows that after the tonic chord in Op. 103, the silence is not on ly perceived to start at a lower level of tension, but is also perceived to decrease dramatically right away: mean sl ider positions move steeply downward across all 1700 ms of the silence. The difference in the shape of tension responses during the two silences sug-gests that not only the absol ute value, but also the time course of musical reactions might differ depending on tonal context.

QUESTIONS (STAGE 3) In Stage 3, participants were asked a number of direct questions about their experience of each excerpt. First, they were asked whether or not they detected a silence in the excerpt. On average, participants detected a silence 95% of the time. The average detection rates for only two excerpts were under 90% : the rate for the

494 E. H . Mmtulis

8 ~ 8 8 ~ 8 ~ ~ ~ ~ ~ Milliseconds from Start of Silence

FIGURE 4. Mean tension slider positions for all participants durinq the silence in an excerpt from a Haydn String Quartet {Op. 103, Movement 1, measure 70). A tonic chord (tonal closure) precedes the silence.

excerpt from the Prelude to Tristan and Isolde (80%), and the rate for the excerpt from the beginning of Chopin's Noctu rne Op. 62 No. I (88%). Both excerpts feature a long, sustained note that fades into the silence, suggesting that listeners may imaginatively project such notes further when they are followed by periods of acoustic silence. Some participants seemed to concep-tualize si lence following long notes as a quiet continua-tion of the previous sound, rather than an actua l silence. This speaks to the innuence of context on such basic sensa tions as: d id I hear a si lence or not?

Participants were also asked to estimate the duration of the silence in each excerpt (see Block & Zakay, 1997, for an overview of the time estimation literature). These estimates were divided by the actual duration of each silence, producing a variable representing the ratio of estimated to actual silence duration: if above 1, the par-ticipant overestimated its length, if below 1, the partici-pant underestimated it. On average, participants overestimated silence lengths; the average estimate-to-actual-duration ratio was 1.48. Contextual factors affected these duration estimates. The lengths of silences following music in a forte dynamic were over-estimated (by 31 o/o) in comparison to silences following music in a piano dynamic, F(1, 24) = 50.33, p < .001. Additionally, the lengths of silences following music that arrived on a predominant harmony were underes-timated (by 28%) in comparison to music that arrived

on a tonic or dominant harmony immediately before the silence, F(l, 24) = 56.75,p < .001. Reaction time data from Stage 1 of the experiment show that participants were late responding to the start of silences when they followed predominant harmonies. Thus, for excerpts featuring a predominant harmony before the silence, listeners may not realize they are experiencing a silence until some portion of it passes, resulting in an experi-ence of silence that seems overall shorter. In contrast, the dynamic level preceding the silence did not seem to affect the response time to silence starts. The increase in overestimation generated by forte dynamics may stem not from an earlier recognition that silence is occurring, but rather from the greater contrast between the acoustic content of the silence and the preceding period. Specifically, the larger decrease in dynamics may have marked the silence more dramatically, resul ting in a sensation of longer duration.

Participants were also asked to estimate the duration of the entire excerpt. These estimates were divided by the actual duration of each excerpt, producing a vari-able representing the ratio of estimated to actual excerpt duration. On average, participants underesti-mated excerpt lengths; the average estimate-to-actual-duration ratio was 0.70. When the estimates of silence length were divided by the estimates of excerpt length, the data reveal that on average participants remem-bered the si lences as taking up 32o/o of the length of the excerpt. In reality, the average silence took up 9% of the duration of the excerpt. Whether this durational infla-tion is a consequence of the focus on silence implied by the experiment, or would occur in more ecologically va lid settings remains open to quest ion. The result may also be an artifact of the already short duration of the silences, which may have made underestimating less likely than overestimating.

In add ition to estimating the duration of the silences and the excerpts, participants were asked to estimate the location of the silence within the excerpt on a scale from 1 to 7, where 1 signified "at the start" and 7 signified "at the end: ' The actual location of the silence was measured by dividing the excerpt duration up to the midpoint of the silence from the excerpt duration in its entirety; the higher this ratio, the closer the silence occur red to the end. Then, a ratio of estimated to actual si lence location was produced by dividing the participant's response by the actual silence location. The greater this ratio, the more participants misremembered the silence as occur-ring closer to the end; the smaller this ratio, the more participants misremembered the silence as occurring closer to the beginning. When the silence followed a predominant chord, participants misremembered it as

having occurred closer to the start of the excerpt than it in reality did, F(l, 24) = 40.65, p < .00 I. When the silence occurred following a tonic chord, participants misremembered it as having occurred closer to the end of the excerptthan it in reality did, F(l, 24) = 37.68, p < .00 I. Since tonic chords often end musical units, and p redominant chords often occur nearer to their begin-nings, these shifts in remembered location might sig-nify a representational real ignment, where the excerpt is remembered as closer to syntactically normative than it actually was.

To assess the metric quality of the different silences, participants were asked whether or not they experi-enced a sensation of beats (or imagined head nods or hand claps) during the silence.3 On average, 32% of participants experienced a sensation of beats during the silent period. For only one excerpt did more than 50% (in th is case, 57%) of participants report a sensation of beats: the excerpt from Beethoven's Hammerklavier Sonata. In this excerpt, a sequence had been established before the silence, consisting of a forte rhythmic gesture followed by a pianissimo echo of the gesture. The silence follows a forte rhythmic gesture, in the space that would normally be occupied by its pianissmo echo. Since th is missing gesture is highly rhythmic and clus-ters around a metric downbeat, it is not surprising that its absence during the period in question resulted in many listeners imaginatively supplying a missing pulse.

Similarly, there were only two excerpts for which fewer than 20% (in both of these cases, 17%) of partic-ipants reported a sensation of beats: the excerpt from Beethoven's String Quartet Op. 131, and the excerpt from Schubert's Moment Musicaux Op. 94, No. 4. In both of these excerpts, the performer decelerates into the rest, which is notated with a fermata. The decelera-tion has the effect of gradually effacing the regu larity of the beat, making it more difficult to mental ly project across the course of silence. Moreover, a fermata often indicates a sort of heatless pause before the regular pulse resumes; observe that in the Beethoven excerpt, the fermata is over a barline rather than over any notated duration. This placement h ighlights the extra-metric quality of that silence.

If participants responded that they had experienced a sensation of beats during the silence, they were also asked to rate how salien t the beats seemed on a scale from I to 7, and to enter the number of beats they imag-ined. The overall mean salience rating was 4.8, and the only individual excerpt mean below 4.0 was that for

3Head nods or hand claps were used in case participants were unfamiliar with the concept of a beat.

Silct~cts ;, Musir 495

Bach's St. Matthew Passion, (3.2). This is not surprising, because that silence falls on the weakest (third) beat of the triple meter, and this beat had not been articulated by a note attack in the melody at any preceding point in the excerpt. Listeners were sensitive to the metrically "unmarked" quali ty of this silence. Contrastingly, the only indiv idual excerpt mean above 5.5 was that for the Prelude to Tristan and Isolde (5.6). Since that silence followed only two notes, the first short and the second qui te lo ng, this result was surprising. One theory about the high beat salience in this excerpt might be that lis-teners, with only one pitch change to cue a beat, count it forward mentally across the long following sustained note and silence, in an effort to make sense of an ambiguous stimulus. The extra effort exerted to attempt to locate a beat in such circumstances (London, 2004) may have been reported by participants as an elevation in beat salience.

Participants were asked to assess how expected the silence was, given the music up to that point. Participants rated the silence as more expected if it was preceded by a chord capable of cadential closure (ton ic or dominant), and less expected if it was preceded by another harmony (predominant), F(l, 24) = 16.45, p < .001. This result is consistent with the idea, suggested also by the results from Stages I and 2 of the experiment, that listeners were sensitive to the normative position of silence after points of tonal closure.

Participants were also asked to assess how expected the music after the silence was, using a scale from I to 7 where I represented "very expected" and 7 "very unex-pected." The mean rating was 3.5. There were only two ratings under 2.5: that for Wagner's Prelude to Tristan and Isolde and Mozart's C Minor Fantasy. In the Wag-ner excerpt, the music after the si lence constitutes a sequential repetition of the music before the silence. In the Mozart excerpt, the music after the si lence consti-tutes a litera l repetition of the music before the silence. Listeners seemed to be sensitive to this patterning, and appeared to interpret it as fulftlling expectations. Silence has a function in grouping (Lerdahl & jackend-off, 1983), serving to demarcate group ends and begin-nings. After the end of one group, a fundamental process of expectation might project repetition of that group. No ratings over 4.5 were given; however one excerpt was assigned a rating of 4.4, indicating that the music after the silence was quite unexpected. In this excerpt from Mussorgsky's Pictures at an Exhibition, the music after the silence features an entirely different tempo, orches-tration, dynamic level, and pitch and rhythmic pattern than the music before the silence. Again, listeners seemed to be sensitive to this distinction.

496 E. H. Mm~ulis

In addition to being asked about the expectations they had sustained during the excerpt, participants were asked to give a retrospective assessment of how well the silence had ftt within the excerpt, using a scale from I to 7 where I represented "very badly" and 7 "very well." The average fit rating across all excerpts was 4.6. Only 2 excerpts received a rating as low as 3.6; one from Beethoven's String Quartet Op. 131 and Bach's St. Matthew Passion. In both excerpts, participants may have been reacting to the silences' unusual emphasis of the measure's weakest beat, and especially to the delay of the subsequent strong beat.

Overall, the results from Stage 3 contribute more evi-dence to the notion that silence perception is shaped in multidimensional ways by the surrounding musical con-text. The questions to which participants responded are exploratory in nature, and merely hint at the complex processing that likely underlies the musical experience of silence. Future studies dedicated specifically to beat per-ception in silences, for example, or to duration estin1ates of empty periods, might provide more robust and detailed accounts of the perceptual mechanisms involved. These data sinlply suggest that the footprint of musical context can be seen with other measures than reaction times and tension ratings. Future studies will hopefully explore th is further.

PARTIC IPANTS

Experiment 2

Method

Twenty-eight participants were recruited from "Introduc-tion to Music" at Northwestern University, as in Experi-ment I. The study took about o ne hour to complete.

Eleven of the 28 (39%) participants reported no music training. Another 12 (43%) reported five or fewer years of instrumental lessons. The remaining five ( 18%) reported between six and ten years of instru-mental lessons. Only two of the participants (7%) reported some training in music theory. None of the participants characterized themselves as musicians, and none were music majors.

The participants reported listening to music between 2 and 28 hours per week (M = 10; SD = 7), and attend-ing between 0 and 12 concerts a year (M = 3; SD = 3).

No participant data was summarily excluded.

MATERIALS The apparatus was the same as in Experiment I . How-ever, Experin1ent 2 used different stimulus materials (see Appendix B). Instead of excerpts from commercial recordings, excerpts were 23 monophonic, diatonic

melodies produced expressly for this study using Adobe Audition. Excerpts lasted between 4 and 9 s (M = 6.6). The silences featured in the excerpts were 0.5 or 1 s long. Excerpts were isochronous with note durations of 0.5, 1, or 1.5 s, except for two excerpts featuring a ritar-dando into the si lence, two excerpts featuring an accel-eration into the silence, and one excerpt featuring staccato articu lations: 200 ms notes interspersed by 500 ms silences. Each individual note in the melody had the same distribution of energy among its frequency com-ponents, as well as the same amplitude envelope. ln an attempt to induce a single metric interpretation for each excerpt, notes falling on metric downbeats were played subtly louder than the other notes (specifically, these notes received a 3 dB boost).

PROCEDURE Procedures were identical to those used in Experiment 1, with one exception. Because the examples were both more uniform (all using the same synthetic tin1bre, for example, versus the diversity among piano, chamber ensembles, and full orchestra in Experiment 1; all using the same monophonic texture vs. the diversity among textures in Experiment I; all using the same two dynamic levels vs. the diversity of dynamics in Experiment I), and less inherently engaging (synthetic excerpts vs. real musi-cal contexts). it was a concern that participants might not attend musically to the stimuli. To encourage them to pay as close attention to the musical content as possible, "checkup" questions were interspersed throughout the reaction time part of the session. These questions asked participants about the contour of the excerpt, the place-ment of its highpoint, and whether the excerpt was new or they had heard it earlier in the session. These questions were intended not to provide data for analysis, but simply to encourage participants to attend to the music rather than simply to scan for the silent period.

Results and Discussion

RTS (STAGE 1) Boxplots were produced for the react ion times to the silence onset and offset in each excerpt. Extreme cases (very late or early responses due to presumed participant error, see criteria for Experiment 1) were removed-on average 2 of the 28 participant responses to each excerpt. One subject (number 6), who complained of exhaustion during the session, performed particularly poorly, and a disproportionate amount of his data was removed. Since the order of presentation (fi rst or sec-ond hearing) d id not affect reaction times to silent onsets or offsets, F(l, 24) = 0.01, p > .05, reaction times from both presentations were pooled and included.

TABLE 3. Mean reaction times and standard error to silence onsets for excerpts in Experiment 2.

Mean RT to silence Standard Excerpt onset (ms) error

I. Accelerando closed 359 22 2. Arpeggios 430 22 3. Accelerando open 494 23 4. Long notes closed 419 22 5. Long notes open 485 22 6. Closed long silence 4t2 22 7. Repeated notes 425 22

strong beat silence 8. Closed short silence 455 23 9. Closed 368 22

10. Repeated notes short 437 23 strong beat silence

tl. Open long silence 452 22 12. Open short silence 495 22 t3. Ritardando closed 350 22 t4. Ritardando open 474 22 15. Repeated notes short 379 24

weak beat silence t6. Repeated notes weak 4tt 23

beat silence t7. Repeated notes 392 22 18. Open 414 21 t9.Sequence 437 23 20. Repeated thirds 424 23 21. Patterned thirds 423 22 22. Repeated note triplets 397 23

Across all excerpts, the mean reaction time to si lence onsets was 437 ms (SO = 70 ms) . The mean reaction time to silence offsets was 462 ms (SD = 80 ms). Although mean reaction times to si lence offsets were comparable to those in Experiment I, mean reaction times to onsets were longer. It is likely that this differ-ence is due to the difference in the re lease characteristics of notes in Experiment I and Experiment 2. All notes in the artificial timbre used in Experiment 2 decayed quickly; however, many notes in Experiment 1 decayed slowly, causing participants often to identify a silence onset before the note had actually ceased completely to sound. This and the greater predictability from excerpt to excerpt, including metric probability, also accounts for the much smaller standard deviation for reaction times in Experiment 2 (see Table 3).

An AN OVA was performed with o nset reaction times as the dependent variable, and pieces (22) and subjects (28) as factors. Reaction times varied significantly across excerpts, F(21, 605) = 3.60, p < .001. A priori

Silct~cts ;, Musir 497

TABLE 4. Mean reaction times and standard error to :silence offsets for excerpts in Experiment 2.

Mean RT to silence Standard Excerpt offset ( ms) error

I. Accelerando closed 471 31 2. Arpeggios 4 t t 32 3. Accelerando open 461 31 4. Long notes closed 462 32 5. Long notes open 402 31 6. Closed long silence 329 34 7. Repeated notes strong 404 32

beat silence 8. Closed short silence 542 34 9. Closed 454 33

10. Repeated notes short 614 31 strong beat silence

I I. Open long silence 599 32 12. Open short silence 414 33 13. Ritardando closed 389 31 t4. Ritardando open 356 35 IS. Repeated notes short 677 33

weak beat silence t6. Repeated notes 375 32

weak beat silence 17. Repeated notes 468 31 18. Open 403 32 t9. Sequence 696 32 20. Repeated thirds 411 33 2 1. Patterned thirds 352 32 22. Repeated note triplets 547 33

post-hoc contrasts were performed to assess the effect of tonal and metric context o n onset reaction times. Since s timuli were isochronous, it was no t possible to assess the effect of long notes as in Experiment I. Some excerpts featured closural movements to the tonic pitch i mmediately p receding the silence, and others featured more open movem ents (such as leaps) to nontonic pitches. If the part of the excerpt immediately preceding the silence ended with closural movement to the tonic pitch, reaction times were significantly faster than other-wise, F(1, 545) = 15.08,p < .001. Although the contexts were impoverished in comparison to Experiment I, they e licited a similar result: reaction times were faster when tonal closure preceded the silence. Unlike in Experiment I, the data in Experiment 2 show no significant effect for t he metric placement of the silence. T he metric con tex-ts may have been too simplified to elicit effects.

An ANOVA was also performed with offset reaction times as the dependent variable, and pieces (22) and s ubjects (28) as factors (see Table 4). Reaction times

498 E. H . M"'gulis

varied significantly across excerpts, F(21, 590) = I 0.04, p < .001. As for the silence onsets, the order of presenta-tion did not affect reaction times for silence offsets, F( 1, 24) = 0.97,p > .05, so reaction times from both presen-tations were pooled and included. When the same two excerpts, differing only in that one achieved tonal clo-sure before the silence and one did not, were played with notes of 500 ms duration and silences of either 500 o r 1500 ms duration, the reaction times to the silence offset were significantly faster after silences of 1500 ms, t(26) = 5.47, p < .001. In other words, reaction times to silence offsets were significantly faster after longer silences, regard less of whether the music pre-ceding the silence was open or closed. There are at least three possible explanations: first, the 500 ms offsets may have occurred while the participants were still recover-ing from the onset response. Second, silences lasting longer than the average note duration may be norma-tive and thus more expected. Third, participants may have targeted their attention at 1500 ms when an offset failed to occur at 500 and 1000 ms.

To distinguish adequately between the possible expla-nations, further research would be necessary. However, the present data allow an exploration of the hypothesis that offset reaction t imes relate to norms of silence placement. Tonal closure tends to demarcate the end of a musical section, and is more often followed by long silences than are other kinds of events. After a melody that achieves closure, listeners should anticipate a longer silence. Although the results are not significant, the data show a trend in this direction. When 500 ms silences were preceded by music that achieved closure, responses to the silence offset were slower than when the 500 ms silences were preceded by music that remained open, 1(26) = 1.98, p = .06. However, when 1500 ms silences were preceded by music that achieved closure, responses to the silence offset were faster than when the 1500 ms silences were preceded by music that remained open, 1(23) = l.19,p = .08. This marginally sig-nificant trend suggest that listeners responded more quickly to long silence offsets when they followed clo-sure, but that they responded more quickly to short silence offsets when they followed openness. This, in turn, suggests that listeners might be sensitive to the nor-mative length of silences in different musical contexts.

Excerpts featuring 500 ms notes and 500 ms silences were contrasted with excerpts featuring 1000 ms notes and 1000 ms silences. The responses to silence offsets were faster for the excerpts where both notes and silences lasted 1000 ms, 1(26) = 4.69, p < .00 I. The same pattern held true for responses to silence onsets, although the trend did not rise to significance; responses were faster

when notes were I 000 versus 500 ms long, 1(27) = 1.89, p = .07. Both these findings are consistent with esti-mates of preferred synchronization rates (Parncutt, 1994). Overall, when the silence length matched the note length (500 or 1000 ms), participants responded faster to the offsets for silences following open music, t(25) = 3.20, p < .005, suggesting that listeners expected silences to be as short as note durations only when clo-sure had not yet occurred.

Analyses were conducted to determine whether the metric placement of a silence (starting and/or ending on or off the beat) affected reaction times to onsets or offsets, as well as whether the meter of the excerpt affected reaction times. No significant effects were found. This supports the idea that pitch contributes more to the conceptualization of s ilence than meter, but it remains possible that another set of more metrically engaging stimuli, with notes and silences of d ifferent, less predictable lengths and more intricate melodic pat-terns would reveal metric effects.

Two of the excerpts featured a ritardando into the silent period. One excerpt achieved closure at the end of the ritardando, and the other remained open. Reaction times to the silence onset for the excerpt whose ritar-dando arrived on the tonic pitch before the silence were faster than reaction times to the silence onset for the excerpt whose ritardando did not, t(26) = 4.38, p < .00 I. Similarly, two of the excerpts featu red an accelerando into the silent period. One excerpt achieved closure at the end of the accelerando, and the other remained open. Reaction times to the si lence for the excerpt whose accelerando arrived on the tonic pitch before the silence were faster than reaction times to the silence onset for the excerpt whose accelerando did not,t(26) = 6.05, p < .00 I. Although ritardandos tend to point to closure, and accelerandi tend to point to continuation, in both cases the arrival of tona l closure seemed suffi -cient to produce an effect, even when temporal evi-dence countered the closural impression (as in the case of the accelerando).

Not only were reaction times to silence onsets faster for tonally closed excerpts regardless of whether the note duration values were constant, increased, or decreased, but also increasing or decreasing the duration values had no discernable effect on the reaction times. In other words, examining just tonally closed excerpts, there was no significant effect on reaction time to the silence onset of approaching it with steady, accelerating, or decelerating note values. This fmding suggests that the tonal schema for silence location is strong enough to override the effects of temporal entrainment (Jones & Boltz, 1989), which would predict that participants

would re;~ct faster to silence onsets in temporally regu-lar contexts.

TENSION (STAGE 21 Since the stimuli in Experiment 2 were more impover-ished, it was uncertain whether systematic tension responses would be elicited. Although the results are not significant,there is a trend in the direction found in Experiment 1, suggesting that basic tonal cues in a rela-tively simple context are enough to activate perceptions of closure and open ness. The first 500 ms of the silence were perceived as less tense if the excerpt arrived on the tonic pitch immediately before the silence, 1(26) = 2.03, p=.05.

Since some note durations were systematically va ried in Experimen t 2, it was possible to examine the effect on tension of sustain ing a note versus following it by a silent pe riod (see Figure 5).

For excerpts ending in an open leap, susta ining the final note over an additiona l 500 ms el ici ted a percep-tion of greater tension increase than when the same 500 ms period was silent, 1(25) = 2.70, p < .05. (This may also have been a function of the slower tempo). For excerpts ending in a dosed arrival on the tonic, no sig-nificant difference e1-nerged betwce1\ sustai1\cd and silent excerpts. This difference in the effect of sustaining a note vs. following it with silence for open and closed excerpts suggests that the time-course over which peo-ple respond to closed and open moments is different. It seems that as soon as the attack for a tonic arrival occurs, participants perceive the tension to drop (com-pare with Figure 4 from Experiment t ). It is equivalent to them whether the tonic note is held or whether silence replaces the hold: in both cases, participants report the tension to drop. When there is an implicative note, continuing to sound it systematically increases the tension. But replacing some of the note's duration with silence does not preserve the effect: the tension fails to

After tonal do sure;

Before tonal c:tosv,.:

N ote

1000 msec

Nolo

1000 msec

500 msec 500 msec

Silence

500 msec 500 msec

FIGUREs. 1000 ms toot and tnt same tone with a 500 ms durallon followed by a 500 ms sltence The two were more perceptually lnter-chanqeable after tonal closurt. and less before it.

Sil.rnc~1 ;, M111ic 499

continue to increase. This finding relates to Frankland and Cohen's (2004) observation that the Attack-point rule, which does not distinguish between held notes and interspersed silences, accounted for boundary place-ments better than any other grouping rule in Lerdahl and )ackendoff ( 1983).11 also relates to the finding from Stage 3 of Experimei\t I (reported above) that listeners were most likely to miss a silence if it followed a long sustained note; there is clearly some blending between perceptions of long notes and silences in some conteX1s.

The two most strongly contrasting excerpts-the excerpt in which the music decelerated to a tonic pitch before the silence (Figure 6), and the excerpt in which the music accelerated to the leading tone (an open pitch) before the silence (Figure 7)-am be compared in terms of the mean positions of the tension slider for all participants across the full 1000 ms of the silence. Not only is the position of each curve different-low for the closed, decelerating excerpt, and high for the open, accelerating excerpt-but also the shape of the curves is different-steeply descending for the closed, decelerating excerpt, and gently arched for the open, accelerating excerpt. After the closed arriva l on the tonic in the excerpt represented in Figure 6, listeners reported an immediate decrease in tension, which was sustained across the course of the silence. However,

100

t c ~ 80 c ..

~

70

60 -

o ' I 0 100 200 300 400 500 600 700 600 900 I 000

Milliseconds from Slart of Silence

FIGURE 6. Mean tension slider positions for all parlc:lpants durlno the silence in an excerpt featurlnq a ritardando to a tonic pitch (closure) before the silence.

500 E. H. MMgulis

100 -

90

c: 0 ;; c: ~ eo-c: .. .. ::s

70 -

60

0 1 00 2()() 300 400 500 600 700 800 900 1 000 Milliseconds from Start of Silence

FIGURE 7. Mean tension slider positions for all participants during the silence in an excerpt featuring an acc-elerando to the leading tone {no closure) before the silence.

after the open arrival on the leading tone in the excerpt represented in Figure 7, listeners perceived the tension to continue to increase across the first half of the silence, but gently curve back down to its preceding level in the second half. These results echo those from Experiment l, shown in Figures 3 and 4.

QUESTIONS (STAGE 3) Participants first reported whether they heard any si lent period in the excerpt. On average, participants reported hearing a silence 92o/o of the time. In one excerpt, 500 ms silences were interspersed among 200 ms notes, making the silences see m more like articulations (con-ferri ng a staccato, truncated quality on the notes) than like marked rests (although in other contexts, the 500 ms silence functioned clearly as rests). For this excerpt, far fewer participants (14%) reported hearing a silence, t(27) = 9.95, p < .001. As in Experiment I, context was able to modulate whether participants perceived a silence or not.

As in Experiment I, participants were asked to rate how well the silence fit wi thin the excerpt. Silences fol-lowing an arrival on the tonic pitch were perceived as bet-ter fits than silences following melodies that remained open, t(22) = 2.83, p = .01. Moreover, when note lengths

remained the same, longer silences were perceived as poorer fits, t(27) = 4.21,p < .001.

Participants were asked whether they experienced a sensation of beats during the silent period. More partic-ipants reported hearing beats during the silence when the excerpt consisted exclusively of repeated notes, t(27) = 2.91, p < .01. Presumably, the absence of complex tonal information permitted a reallocation of atten tion to the basic rhythmic qualit ies of the excerpt. Moreover, because the melodic contentr in these excerpts was com-pletely predictable (merely repetitions of a single note), participants may have imaginatively extended it across the course of the silence. These imagined notes may have marked time in a way that led to the reporting of a salient sensation of beats.

Participants rated silences as more tense when they followed a tonally open segment even if the tempo was changing (i.e., the music was accelerating or decelerat-ing}, t(26) = 3.01, p < .OJ. The same effect held for excerpts where the silence was 1000 ms and the notes were 500 ms, t(24} = 2.43, p < .05. The same direction of effect occurred for all other excerpts, but was not significant. It may be that the 1000 ms silence allowed more time for the difference in tension to noticeably emerge, particularly given the results from the ten-sio n portion of the study suggest ing that the time scale of tension changes differs after closed and open excerpts.

Participants were asked to estimate the duration of the silence. These estimates were divided by the actual silence durations to produce ratios reflecting the degree of over or underestimation. Because all excerpts except the four featuring a ritardando or accelerando wee isochronous, it was hypothesized that temporal infor-mation would be clearer and estimates would be more accurate. Indeed, estimates were more accurate than in Experiment I, but sti ll reflected an inflation of the silence's duration in memory. On average, participants estimated silences to be J.J6 times as long as they actu-ally were (as opposed to 1.48 times in Experiment 1). As in Experiment I, silences occurring immediately after the arrival of tonal closure were estimated as lasting longer than silence occurring after music that remained open, t(22) = 2.14, p < .05. Given the results from the reaction time portion of the study, th is difference is the-orized to arise out of the faot that it takes listeners some time to acknowledge that a silent period has actually begun when no closure has yet occurred.

ln comparison to Experiment I, participants were also more accurate in judging the lengths of excerpts, slightly underestimating them as .97 times the length

they actua lly were. vVhen the estimates of silence length were divided by the estimates of excerpt length, the data reveal that on average participants remembered the silences as taking up 26o/o of the length of the excerpt.ln reality, the average silence took up 15o/o of the duration of the excerpt. As in E:-.-periment 1, these data show an inflation of comparative silence length in memory, though not as extreme an inflation.

Overall, results from Stage 3 in Experiment 2 mirror those from Stage 3 in Experiment 1, but without as much richness and subtlety; a consequence of the starker, simpler musical contexts.

General Discussion

Several general trends emerged across both ex peri-ments. First, and most generally, musical context affects the perception of silen t periods, themselves devo id of any presently sounding stimulus. Second, silence is affected not only by the temporal context surrounding it, but also by the pitch context preceding it (although silences themselves contain only temporal information: the length of their duration). Third, the occurrence or nonoccurrence of tonal closure (in the form of a melodic descent to the tonic pitch, o r a cadential arrival on the tonic chord) immediately before the silence is perhaps the most significant factor in the shaping of that silence's sound.

Silences often occur at phrase boundaries in both lan-guage and music, allowing time for listeners to shift attention from one syntactic unit to the next (Knosche et al., 2004). Yet they can also occur mid-phrase, at points of dramatic tension or interruption (Dougherty, 198 1 ). This study shows that listeners responded d iffer-en tly to these silences, reacting to them more slowly, and experiencing a different flow of musical tension across their duration. Overall, it provides additional evidence that the time course of musical engagement is complex; elements from the past (e.g., preceding musi-cal context) impact significantly on the experience of the present (e.g., a presently sounding silence), such that a silence within one context is not really experi-enced as the same event as that silence in another con-text. It remains an intriguing topic for further inquiry how precisely th is web of remembering and expecting applies in musical listening, and in e:-.-perience at large.

These results also add support to the growing body of evidence that listeners implicitly extract stylistic norms from the corpuses of music they encounter. Participants in th is study had little or no musical training, and yet

Silct~cts ;, Musir 50 I

proved highly sensitive to subtleties regarding the con-textual placement of si lence. Statistical learning has been proposed as a mechanism to account for this kind of implicit enculturation (Saffran, Johnson, Aslin & Newport, 1999). It is particularly noteworthy that responses reflective of stylistic norms were elicited not only by full musical excerpts, but also by starkly impov-erished excerpts possessing only the barest rudiments of tonal structure. Precisely what (or how little) is required to persuade listeners to " respond musically" (where "respond musically" means cognitively to activa te a particular set of schemas and ex-pectations, and physio-logically to activate particular neural circuitry)?

People have hypothesized that part of the nature of a "musical" response is its partial ineffability (Raffman, 1992). The responses to silence made during th is study were complex and consistent across a population of untrained participants, yet ordinary conversation would Likely not reveal that these moments had partic-ularly engaged the listeners. Indeed, as Bent (1981) observes, even the terminology trained musicians use to discuss silence implies that it is little more than a nonentity, a blank canvas on which the notes are drawn. The results from this study, however, suggest that silences are loci of active musical engagement. What cognitive mechanisms underlie the projection of musi-cal expectations that produce stable measures (such as reaction time and tension assessments) of active pro-cessing during silen t spans but seem not to rise to the level of direct reportability? What does it mean that people seem to respond musically even when they don't know they're doing so?

Silent periods embody an opportunity to study the active, participatory nature of musical engagement. Although very little empir ical litera ture has so far exploited their potential, silent periods could provide a unique chance to study the way that past musical events shape expectations about future ones, and the way that underacknowledged, often taken for granted musical elements (such as rests) are actually suffused with the li.11l extent of "musical" listening. The Due de Ia Rochefoucauld made a tell ing observation about speech: silences might be "eloquent," "mocking:' or "respectful:' he said, and mastery of such "airs and tones" is only "granted to a few" ("The Chattering Classes;' 2006). Just as the keys to the social relationships in a 17th century salon might be unlocked only by careful attention to the most inconspicuous of conversational elements--the pause-the keys to the nature of musical attending might be found most readily in the places where the notes stop.

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502 E. H. M"'gulis

Author Note

The author would like to thank the Northwestern Univer-sity School of Music for support of this project during the data collection stages, when the author was on the School of Music faculty. The author would also like to thank Christopher Rhoads for statistical consultation

on the project, and David Huron for providing a cor-pus analysis of rests in the Essen Folksong Collection.

Correspondence concerning this article should be addressed to Elizabeth Hellmuth Margulis, University of Arkansas Department of Music, 201 Music Bldg, Fayet-teville, AR, 72701. E-MAIL: ehm@uark.edu

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