drum-pattern-engine (JS)

Universal drum-pattern + song-arrangement generator. No runtime dependencies.

The engine is device-agnostic: it emits a neutral song structure (instrument roles, steps, velocity, micro-timing, bars, repeats, meter). A separate builder package turns that into a concrete device format — e.g. smpltrek-builder writes a Sonicware SmplTrek project. The same song could drive MIDI, another groovebox, etc.

This is the single source of truth for the engine; the Python port (drum-pattern-engine-py) is kept byte-identical via a parity check.

Install

npm install drum-pattern-engine

Usage

import { arrange } from 'drum-pattern-engine';

const params = { density: 0.6, instrumentDensity: 0.65, energy: 0.75, swing: 0.15, ghost: 0.3 };
const song = arrange(params, { length: 'full', bpm: 124, seed: 12345, structure: 'electronic' });
// hand `song` to a builder, e.g. smpltrek-builder's buildProject()

The song structure (the reuse interface)

arrange(params, opts) returns:

{
  clips: [{
    idx, name, role, repeat, intensity,
    pattern: {
      steps: [{ step, inst, velocity, micro }],  // inst = role string; velocity 0..1; micro = timing offset in step-fractions
      bars,            // bars in the clip
      stepsPerBar,     // 16 for 4/4 at 1/16
      note,            // note-resolution code (default 9 = 1/16)
      timesig,         // time-signature code (2 = 4/4)
      role
    }
  }],
  bpm, totalBars, seconds, params
}

inst is a role (kick, snare, hat, ohh, ride, crash, tom1, perc, …) — not a note. A builder maps roles to notes. note/timesig use SmplTrek's index encoding today (a small coupling that a future version may make fully semantic).

Other exports: generatePattern, generateFill, engine (namespace).

Parameters (0..1)

density, instrumentDensity, syncopation, swing, complexity, energy, humanize, predictability, fillProbability, turnaround, densitySpread, ghost, oddMeter.

Options

length (loop/short/full), bpm, seed, structure, feel, meterMode, meterSet.

Develop

npm install        # eslint + prettier
npm run format
npm run lint

Legal

SmplTrek and Sonicware are trademarks of Sonicware Inc. This is an independent, unofficial tool — not affiliated with, endorsed by, or sponsored by Sonicware.

License

MIT — Alexander Schornberg.