Sample Playback Synthesis

Record one real note, then stretch, loop and pitch it across the keyboard.

Related

SamplerTimbreSamplersModern

The question

A sampler holds a handful of recorded notes, yet every key sounds and still reads as the original instrument. How does one note become a keyboard?

How it works

Recordings are divided into key zones and velocity layers, each holding one or more samples. A keypress selects a sample, then playback speed changes in proportion to pitch, so pitch, duration and resonance all move together. To save memory, sustained notes loop between loop points; misaligned points produce pulsing. Zones are joined by crossfades, which blur if too long and expose a seam if too short. The synth then adds filtering, envelopes and effects to hide the artefacts of transposition.

Settings and what you hear

The further a sample is transposed, the more it resembles an accelerated recording, short and shifted in resonance. Loop points close to the attack make the tone tight, while points near the tail expose the cycle. Few velocity layers mean loudness alone carries the accent, without real colour change. Filtering can tame the bright edge of transposition, but too much removes the instrument's body.

What to listen for

Hear a piano's upper register: the attack still reads as piano, but the tail is shorter than below. Then hear a nylon-string guitar, where the finger noise differs slightly on every note. Finally hear tubular bells and check whether the long decay pulses at the loop.

Common misconceptions

That sample playback is merely pressing play on a recording; that one sample can cover the whole keyboard; that loop points and velocity layers hardly affect realism.

Sources

• Curtis Roads, The Computer Music Tutorial — sampling and playback checked, not quoted
• MIDI Association, General MIDI 1 Sound Set — program list checked, not quoted

Used for fact-checking only; all prose is original.