Interfacingthetxalaparta:digitisingatraditionalinstrumentwiththehelpofitsplayers

EnrikeHurtado

UniversityoftheBasqueCountry,Bilbao,Spainenrique.hurtado@ehu.eus

Abstract.ThispaperdescribestheprocessofcreatingsoftwareforgenerativemusicthatincorporateskeyelementsoftheBasquetxalapartainstrument.Thisispartofanongoingresearchprojectwhichstudiesthisancientmusicaltradition.Traditionally,thetxalapartaisplayedasimprovisationbyatleasttwoplayersandinthisresearchprojectwehavedevelopedasystemthatallowsaplayerandacomputertoplaytogether.Thispaperdescribestheuser-centeredapproachinthesoftwaredesignexplaininghowthisinfluencedthesolutionsandissuesaddressed.Theresearchwaswidereachinginitsuserstudies,anditprovideduswithadeeperinsightonthetxalapartaplayandthe-implicitorunexpressed-rulesinvolvedintheinteractionbetweenplayers.

Keywords:txalaparta,generative,interface,interaction,participatorydesign.

IntroductionThetxalapartaisapercussiontraditionoriginalfromtheruralareasoftheBasqueCountry.Theinstrumentbelongstothecategoryofstruckidiophonesandconsistsofavariablenumberofwoodenplanksplacedhorizontallyontwotrestles,andbeatverticallywithrelativelyheavywoodenbatons.Planksmadeoutofothermaterialssuchasironorstonearealsocommon.Thetxalapartaisplayedbyatleasttwoplayerswhoalternatetheirbeatstoconstructthebarperformingthroughanimprovisatorycall-and-responsepattern.

Thetxalapartaandtheavant-gardewererelatedduringthe60sand70s(Hurtado,2015a),andlikemanycontemporarymusicalcompositionssincethe50s,itsplaycanbeunderstoodasaprocessdefinedbyaseriesofinstructionsthattheplayersuseasguidelinetoimproviserhythms.Infact,manyauthorsandinterpretersclaimthatwhenreferringtothetxalapartawearediscussingtherulesandtherhythmgeneratedmorethanthephysicalinstrumentitself(Escribano2012,4;Beltran1988,198).

Sincethelate80s,theinstrumentandthewayitisplayedhaveundergoneanormalizationprocess,called“xylophonisation”byEuba,whereitstraditionalpercussivenaturehasshiftedtowardsamelodiconewiththeplanksbeingtuned(2004,32)andtherhythmaccommodatedtothestandardwesternmusiccanon.However,theoldstyleofplayingisstilllearntandusedbymany.

BackgroundThetxalapartahasnotbeenthesubjectofacademicresearchuntilveryrecently.Escribano(2012)andGambra(2008)haveexploredculturalandacousticalissueswhileEuba(2004),andSanchezandBeltran(1998)havefocusonthemusicalaspect.Also,somepractitionersprovideanintroductiontotheplayinganddescribetheinstrumentandthetraditionsaroundit(Beltran2004;Beltran,2009;Goiri,1996)andtherearereferencesfromanthropologistsandmusicologistsatthebeginningoftheXXcentury(Azkue1906;Lecuona1920;Donostia1924;Barandiaran1934).

Figure1.TheUgartebrothersplayingtxalaparta.PicturebyXabierEskisabel

Someattemptstoproducesoftwarebasedonthetxalapartahavebeendevelopedbeforeus.Intheearly90s,TecnotxalapartawasdevelopedattheLaboratoriodeTratamientodePalabrayMúsicainMadrid.Thissoftwarewasabletolistenandrespondtothehumaninterpreteradjustingitstempoinreal-time.TheinputwasdonewithkeystrokesinakeyboardandthecomputeroutputwasMIDI.Tecnotxalapartawasneverreleased.Later,Ixiaudioreleasedanapplicationwherebydraggingfoursticksaroundtheinterfacetheuserwasabletocontrolanongoingtxalapartarhythm.Morerecently,appearedTtakun,asequenceraimedatcreatingcompositionsandexercisesforthetxalaparta.Finally,TxalapartappfortheiOSallowsoneormanyuserstoplaytxalapartabytouchingthescreen.Therearealsoprojectssimilartooursbutthatfocusonotherinstrumentsandtypesofmusic.Tonamesome:TheContinuator(Pachet2002),ImprovGenerator(KitaneandKoike2010),GenJam(Biles2002),Haile(Weinberg,DriscollandParry2005),RoboticMarimbaPlayer(WeinbergandDriscoll2007)orShimon(HofmanandWeinberg2011).OtherrelevantprojectsfocusonpopularmusicfromEthiopia(Herremans,Weisser,SörensenandConklin2015)orTalmusicfromthenorthofIndia(WrightandWessel1998).

Softwaredevelopment:ResultsWetriedtounderstandandformalisetherulesofthetxalapartaplayandtodevelopsoftwarethatreflectsthose.Weaimedatproducingapplicationsthatcouldrunonastandardlaptopsandtheresultwastwodifferentpiecesofsoftware.Thefirstone,calledAutotxalaparta,isasemiautomaticgenerativesoftwarethatfollowssimilarrulestothoseusedbytxalapartainterpreters(Hurtado2015b,124).Itgeneratesbothpartsofthetxalapartarhythm(thetwoplayers)andagraphicalinterfaceallowstheusertocontroldifferentparametersoftheprocess.TheAutotxalapartacanalsobeusedtoproduceonlyonepartoftherhythmthusallowingtoplayarealtxalapartaontop.However,thereisnointeractioninvolvedandthehumanhastofollowthemachine.Wedevelopedasystemtosequenceandautomatethemainparametersinthesystem.Thisallowedformorecontrolbutitdidnotallow,either,forrealtimecontrolwhileplaying.

Figure2.TheInteractivetxalapartasoftware

ThesecondsoftwareiscalledInteractiveTxalaparta.Itlistenstothehuman’splayinatxalapartausingthemicrophoneinputanddistinguishesthedifferentphrasesplayed,infersthetempoandprovidesresponsesthatfollowthehumanplay.Italsodetectsthenumberofhitsoneachphrase,theamplitudeofeachhit,theintervalbetweenhitsandwhichplankeachhitstrikes.ThesystemrespondstothehumanusingdifferenttechniquessuchasMarkovchainsandweightedrandomchoices.TheMarkovchainshaveoftenbeenusedtogeneratemelodies(Patchet2002),butheretheyareusedtodeterminethenumberofhitstheanswerphraseshouldcontain.Weightedrandomchoicesareusedtodecidewhichplanksareplayedintheanswer.Answerscanbebuiltintwomodes,thefirstonebuildsthephrasebygeneratingitsvalues(amplitude,intervals,etc...),whilethesecondonereusesinformationfrompreviouslyplayedphrases,thusbeingmorerealistic.Bothmodesfollowtheplayer'slastphrase’smeanamplitudeandmeanintervalsbetweenhits.Bydoingsothesystembehavesclosetohumanplayers,whoareinconstantnegotiationtokeeptherhythmgoing.CurrentlytheInteractiveTxalapartadoesnotproposenewideasorsituationsasitsmaineffortistoadaptandfollowthehumanconsistently,stillbeinglimitedinthestylesoftxalapartaplaythatcanunderstandandproducetorespond.Theinformationwiththeplayedphrasescanbesavedintoatextfileallowingforlaterfeedingtheapplicationwithdatathatreflectscertainplayingstylesorrules.

ParticipatorydesignandfeedbackfromplayersTxalapartaplayershadanimportantroleinthedevelopmentaswecontactedthemfromveryearlyonintheprocesstogetfrequentfeedbackonthesoftware,butalsotolearnaboutthelatesttrendsontxalaparta.Welookedforexperiencedplayerswithanopenmindedattitudetowardsnewideasandinnovationsandwescheduledmeetingsatkeystageswithintheprocess.Themeetingswerelaidbackonetoonetalkswerewereviewedthecurrentstateofthesoftwareandtesteditoutwhilewritingdownideas,suggestionsanderrorstheplayerwouldpointout.Occasionallywemadechangesinthecodeinsitu,iftherequestortheerrorweneededtosolvewaseasytoimplement.Wetriedtogetplayersinvolvedinthedevelopmentasmuchaspossibleandoneofthemactuallyattendeduptofourofthosemeetingsatkeypointsintheprocess.

Figure3.BeñatIturriozplayingwiththeInteractiveTxalaparta

Asaresultofthisuserorientedapproachwedetectedandfixedmanybugsandproblemsinthesoftware,butmoreimportantly,weidentifiedkeyideasthat,webelieve,wewouldhaveneverforeseenotherwise.Forinstance,duringtheearlydevelopmentoftheAutotxalaparta,playersexpressedtheirinterestinimprovisingtxalapartawiththecomputerassecondplayer,somethingwesimplydidnotexpect.LatertheypointedoutthattheyfeltstructuresgeneratedbytheAutotxalapartaweretoorandomand“nonhuman”.Torespondtothisissue,wedecidedtodevelopasystemthatwouldadapttothehumanallowingforaninteractiveimprovisatoryplay:theInteractiveTxalaparta.Inthiscasetherealinstrument,thetxalaparta,effectivelybecomestheinterfacetocontrolthesoftware,asthesoftwareadaptstothehumanplay.TheInteractiveTxalapartawasadirectconsequenceofthefeedbackandtherequestsreceivedfromtxalapartaplayers,anditmighthaveneverbeenenvisionedotherwise.

Apartfromtheinvaluablefeedbackonthedevelopmentcyclewejustbrieflydescribed,themeetingsprovideduswithaveryinterestinginsightonthetxalapartaplay.Theyshapedourunderstandingofthetxalaparta,butmoreinterestingly,theyalsoshapedtheunderstandingoftxalapartathatplayersthemselveshad.Thefactthatplayerswere,forthefirsttime,improvisingwithamachineinsteadofahuman,madethemself-awareandconsciousofmanyaspectsofthetxalapartaplay,andthewayplayersinteracttoeachother,thatwerepreviouslytakenforgranted.Theysaidtheyfounddistressing,forinstance,notbeingabletoseethearmsandbodyofthesecondplayer.Thisseemstobecrucialforthetxalapartaplayastheyrealisedtheyforeseetheactionsofthesecondplayerinthepositionandmovementofthebodyandarms.Inourcase,becauseoftheabsenceofabodywhileplayingwithacomputer,theysometimesfoundtherhythmgeneratedbythemachinedifficulttounderstand.Thisissueinfluencedthesoftwaredevelopment:toovercomeit,wedesignedgraphicalrepresentationsofthecomputer'srhythm.Themaingraphicalaidsdevelopedareacircularanimation1thatrepresentstheeventsplayedinthecurrentbarandapiano-rolltimeline.Inthefirstonethecurrentbarisrepresentedasacirclewiththephrasesofboththehumanandthemachinebeingdisplayed,thehitsdrawnasdotsfollowingclock-wisedirection.Sizerepresentsamplitude,positionrepresentstiming,humanproducedhitsareredandmachinehitsareblue(seecirculargraphicinthecentreoffigure2).Thesecondgraphicalaidisapiano-rolltimelinewherethepercussiveeventsanditsmaincharacteristics,suchasplayer,amplitude,timeandplankaredisplayedinreal

1InspiredonadiagrambySanchezandBeltran(1998)

time(seetoppartoffigure2).FuturedevelopmentsshouldincludethepossibilitytosavethedatadisplayedinthetimelineasMIDIforfurtheranalysisortobeusedwithinasequencer.

Playerssaiditwasveryinterestingtoplaywithbothprogramsbutintheiropinionthesoftwareisstillquitelimitedstylistically,astheInteractiveTxalapartacanonlyunderstandacertaintypeoftxalapartastyleandrhythms,andbothprogramscanonlygeneratealimitedstyleoftxalaparta.Weobservedthatsomeinterpretersoccasionallyusedthesoftwaretogetresponsessuchthatnohumanwouldproduce.Theyalsoplayedaroundwiththeerrorsthesystemproduced.Theseplayerssaidtheyfoundstimulatingwhenthesoftwareplayedclosetothelimitsofwhatcanbeconsideredavalidtxalapartarhythmorwhenitdidsomethingthatnotxalapartaplayerwouldeverdo.WepresentedanearlyversionoftheprogramsattheTxalapartaConferenceinPamplonainMarch2015wheremostattendantsthoughtthesoftwarewouldbeusefulbecauseitallowstoimprovisetxalapartawithoutasecondplayer.Attendantswerealsoveryinterestedinthequestionsonthenatureofthetxalapartaplaythatthesoftwareraisesandthathavepointedoutabove.Finally,wewouldliketomentionthatinthisongoingresearchontxalaparta,wehavecarriedoutthefirsteversurveyonit.Thiswasanonlinesurveywithquestionsonthetxalapartaandthechangesithasundergone.Itmainlyfocusedonqualitativedataandprovidedusveryinterestingdatathatcomplementedmanyaspectsofourresearch,butthatfalloutofthescopeofthispaper.

ConclusionsandfutureworkWehaveproducedtwocomputerprogramsbasedonthetraditionaltxalaparta.Oneofthem,theInteractiveTxalaparta,canbecontrolledbyplayingarealtxalapartaandallowsplayers,forthefirsttime,toimprovisetxalapartawithacomputerasthemachinegeneratesresponsesthatfollowtheuser’splaywhilelearnsandadaptstoit.Thecloseinvolvementoftxalapartaplayersduringthedevelopmentprovedcrucialasitallowedustoreachunforeseenresultsaswellastoidentifykeyideasandconceptsonthematter.Thisalsoprovideduswithadeeperunderstandingofthetxalapartaplayanditsmaincharacteristics.Futureworkshouldincludethedevelopmentofmorefunctionalandcompletesoftwarethatwouldallowtoanalysefurtherthetxalapartaplay.Thisshouldimprovethealgorithmsthatanalysethehumanplaytoallowformorestylesoftxalapartaandrhythmicaltechniquestobeunderstoodbythesystem.Wewillalsoimprovetheanswersystemtogeneratemorecomplexandrichrhythms,aswellasclosertothecomplexityofthehumanplay.Weplantoproduceacrossplatformversionoftheprogramsthatwouldallowustoreachabiggernumberoftxalapartaplayers.Thiswouldprovideuswithamorevariateandsystematicfeedbackfromtheplayersonthesoftwarewehavedeveloped.

AcknowledgementsThisresearchhasbeenpossiblethankstothesupportoftheElhuyarandtheUniversityoftheBasqueCountry(theArtandTechnologyDepartmentandtheMikelLaboaKatedra).

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