Building a whole track: arrange()

arrange() is the backbone of a multi-section song: each entry is [cycles, pattern], sections play back to back for their spans of whole cycles, and the whole arrangement loops once the total is reached.

A small worked example — 4-cycle intro, 8-cycle verse, 4-cycle outro, reusing the harmony-section patterns:

import { arrange, chord, n, note, stack } from '@liminal-hq/undertone';

const progression = chord('<Dm9 BbM7 Gm9 A7sus>').voicing().sound('sine').sustain(0.8).gain(0.35);
const bass = note('<d2 bb1 g1 a1>(3,8)').sound('square').sustain(0.2).lpf(500).gain(0.5);
const melody = n('<0 2 4 5 4 2 1 0>*2 ~')
  .scale('d5:minor')
  .sound('triangle')
  .sustain(0.25)
  .gain(0.3);

const intro = progression;
const verse = stack(progression, bass, melody);
const outro = stack(progression, bass);

const song = arrange([4, intro], [8, verse], [4, outro]);
const handle = song.loop({ bpm: 96 }); // 16 cycles ≈ 40 s per pass, then round again

Each section experiences its own cycles starting from zero whenever its span begins: the verse's <Dm9 BbM7 Gm9 A7sus> alternation always opens on Dm9, no matter that the verse starts at overall cycle 4. That makes sections self-contained — you can develop each one on its own with .loop() and then slot it into the arrangement without its alternations shifting.

Since arrange() returns an ordinary pattern, everything composes as usual: arrange(...) inside a stack() (a drum loop that runs under every section), .fast(2) on a whole arrangement, or an arrange() section that is itself an arrange().