granular

Granular — Granular synthesis engine. Slices a sample buffer into tiny grains and re-synthesises them with controllable position, density, scatter, and pitch.

Quick Start

granular({ url: './sample.wav', grainSize: 0.08, density: 12 })

Parameters

Name	Type	Default	Range/Options	Description
url	string	—	—	音声ファイル URL (CORS 必須)
grainSize	number	0.08	0.01–0.5 s	グレインの長さ
density	number	12	0.5–100 grains/s	1秒あたりのグレイン数
scatter	number	0.3	0–1	タイミングの散布量 0–1
position	number	0.5	0–1	バッファ内の再生位置 0–1
positionVar	number	0.1	0–1	再生位置の揺らぎ 0–1
pitch	number	0	-24–24 semitone	ピッチシフト 半音単位
gain	number	0.7	0–1	出力ゲイン

How it works

On each play() call, granular schedules multiple BufferSourceNode triggers over the note duration. Each grain:

• starts at a position in the buffer determined by position ± positionVar
• has a duration of grainSize seconds
• is windowed with a Hann-style amplitude envelope to avoid clicks
• is spaced 1 / density seconds apart, with optional scatter jitter

Examples

Ambient cloud texture

function* song(ctx) {
  const key = scales(8, 'E3:dorian')
  const g = granular({
    url: './pad.wav',
    grainSize: 0.18,
    density: 20,
    scatter: 0.8,
    position: 0.4,
    positionVar: 0.3,
    gain: 0.6,
  })
  chain(g, reverb({ size: 1.2, mix: 0.6 }))
  yield cast(g, key, seq(8, '\{0,4\},~,~,~,~,~,~,~'), ctx)
}

Slow position sweep over time

function* song(ctx) {
  const pos = (ctx.cycle % 32) / 32  // scan 0→1 over 32 cycles
  const g = granular({ url: './drone.wav', grainSize: 0.12, density: 16, position: pos, gain: 0.5 })
  yield cast(g, scales(4, 'C3:minor'), seq(4, '0,~,~,~'), ctx)
}

Combined with stutter

const g = chain(
  granular({ url: './loop.wav', density: 8, scatter: 0.5 }),
  stutter({ rate: 16, duty: 0.4, mix: 0.6 }),
  reverb({ mix: 0.4 }),
)