sampling-1 intro

SAMPLING

Sampling …the most ubiquitous synth engine

• What is a Sampler?• How does it differ from a subtractive

synthesizer?• Special Sampling Terms

Week 5

reminder… BASIC SYNTHESIS

Source

Modifiers

AudioSignal Processors

Function Generators

MIDI

- Pitch of Note- Velocity of Note- Duration

SAMPLING

Source

Modifiers


Function Generators

MEMORYMIDI


Can we just replace the source with an instrument recording…?

Note Pitches, Tone Color and Shape

Source Osc Frequency

Frequency Multiplier

Audio

MIDI

Pitch of Note eg: C4

MIDI


But remember, the oscillators are buzzing away continuously – envelope generators shape the individual notes, and filters control aspects of tone color.

SAMPLING

Source

Modifiers


Function Generators

MEMORYMIDI


The basic principle of sampling seems straightforward, but there are questions…

How to extend the wave and deal with different pitches?

Source Osc Frequency

Frequency Multiplier

Audio

MIDI


MIDI


Source

MEMORY

The sound of real instruments…

Source

MEMORY

Source

MEMORY

Does a piano, for example, just make one unique sound…?

The “PERFECT PIANO SAMPLER”

For the “Perfect Ultimate Piano Sampler”…

1. We’ll need a recorded sample of each of the piano’s 88 keys, (BTW: a piano’s low key can lasts 50 seconds when struck and sustained, a high key about 5 seconds so the average length would be about 25 seconds).

2. Let’s say an average pianist wants to hear 4 levels of dynamics – soft, low-mid, hi-mid and loud. That makes it 4 samples per key.

Total number of seconds of recording…

88 x 25 x 4 = 8,800 secs

That’s nearly two and a half hours of recorded samples…!!

Back to the real world…

Can sampling be more efficient…?

1. Do we need to have a sample for every key? Not necessarily2. Do we need a separate sample for every dynamic layer? No3. Do we need to record the whole natural length of a note? No

So, yes it can be more efficient by…

4. Extending shorter sample recordings by looping5. Using samples over limited keyboard ranges (multi-sampling)6. Using filters to replicate the effect of dynamics

Sampling - looping

Start with our original wave – for example a long piano note

Sampling - looping

First, we have to find a small portion of the wave that will loop smoothly. With musical instrument sounds this can usually be found after the initial transient has passed and the sounds decay settles down

Sampling - looping

The sampling “engine” can now continuously repeat the section of the wave selected for looping. Tools such as crossfading can make the looping smooth. We now have a wave that will sustain forever…

Sampling - looping

The final step is to apply an amplitude envelope – just as we do with the standard synthesizers.

Sampling - multisampling

Why do we need different samples for different pitches? Can’t the sampling engine multiply the frequency to get the pitch of any note, like the basic synthesizer…?

With the basic wavetable synthesizer, the oscillator was producing a very simple wave which has the same timbral characteristics at all pitches. Real instruments essentially make different sounds at different pitches, so simply multiplying the frequencies in the sampling engine to get different notes from one instrument sample, simply doesn’t work very well.

A look at the spectrum will help explain why, then let’s listen to an example…

Sampling Pitch Engine

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

Resonant or formant peak

X 2

Sampler “pitch engine”

Real Piano Note

B3

Real Piano Note

B5

Sampler Note

B3

Sampler Note

B5 B5B3 ( / 4) ( x 4)

Sampling – multi-sampling

Multi sampling is about using a single sample across just a limited number of keys – usually called a zone – where the effects due to the sampling pitch change are acceptable

Sample-1 Sample-2 Sample-3 Sample-4 Sample-5

Sampling – Filter for dynamics

We saw with basic synthesis that the filter can be used to make a sound brighter or more mellow by subtracting overtones or harmonics from the original sound.

By linking the filter cutoff frequency and the overall amplitude, to the velocity (dynamic) of the note, we can simulate the effects of loud and soft playing.

Play Loud

Play Soft

filter open

filter closed

Sampling – velocity layers for dynamics

A more sophisticated (and true to the principles of sampling) method of introducing dynamic timbral behavior based on effort or force, is to use “velocity layers”…

Sample-1v1 Sample-2v1 Sample-3v1 Sample-4v1 Sample-5v1

Sample-1v2

Sample-1v3

Sample-2v2 Sample-3v2 Sample-4v2 Sample-5v2

Sample-2v3 Sample-3v3 Sample-4v3 Sample-5v3

play harder

Drum Machines & Groove Loops

Others applications of sampling.Originally, sampling was seen as a synthesis method that enabled the realistic synthesis of acoustic instruments and sounds, and it remains the most common method of synthesis today for these purposes.

However, musicians and engineers soon realized that multi-sampling does not need to be restricted to the sounds of one instrument, like a piano. For example - drum machines work on the basis of putting a separate drum sound (snares, toms, cymbals, blocks and so on) on different keys, allowing a “multi instrument” to be played at one time from a keyboard.

In addition, playing back wave loops with a synthesis engine works just as well for longer rhythmic wave files as with the small sustained portion of acoustic instrument sounds. And so groove looping was born...

Sound Libraries

Special case of sampler content.Sampler sound libraries are slightly different to synthesizer patches because they contain two distinct types of files

1.The parameters and settings of the sampling/synthesis engine – equivalent to the patches and programs associated with subtractive of other types of synthesizers

2.The instrument source files - samples and multi-samples

whereas a synthesizer patch might contain instructions like “Set the controls like this and set the oscillator source to a sawtooth wave” a sampler patch might say “Set the controls like this and use those samples, stored in that folder, as the source wave for each keyboard zone”

Summary

Samplers are Synthesizers. They use a wide variety of digital audio as the wave source. It is important to understand these facts about samplers…

1. Samplers use a source wave file, called a “sample” as the basis of a sound. This sound (if musical) will have an original key.

2. For realism, it is necessary to sample instruments at different pitches and make multi-samples with different samples attached to different zones of the keyboard (or pitch range of the instrument)

3. Samplers can make use of filters and other synthesizer controls, just like subtractive synthesizers

4. Voice libraries for samplers include the program parameters and the sample files

sampling-1 intro

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