Getting Started

MIDI Sketch is a lightweight library for auto-generating pop music MIDI sketches. It runs entirely in the browser using WebAssembly.

New to music theory?

If terms like chord progression, key, or motif are unfamiliar, start with the Course — it teaches the music basics behind every MidiSketch setting, with playable notation examples.

Quick Start

BETA

The npm package is not yet published. During the beta period, please use the library via the demo page or build from source. See Installation for details.

import { MidiSketch, init, createDefaultConfig, downloadMidi } from '@libraz/midi-sketch'

// Initialize the WASM module
await init()

// Create an instance
const sketch = new MidiSketch()

// Create a config for a style preset (0 = first style)
const config = createDefaultConfig(0)

// Customize as needed
config.key = 0           // Key (0 = C)
config.bpm = 120         // Tempo (0 = use style default)
config.seed = 12345      // Random seed (0 = random)

// Generate MIDI
sketch.generateFromConfig(config)

// Get the MIDI data
const midiData = sketch.getMidi()

// Download the file
downloadMidi(midiData, 'my-song.mid')

What It Generates

MIDI Sketch generates multi-track MIDI files with:

Track	Channel	Description
Vocal	0	Main melody line (piano roll-safe)
Chord	1	Harmonic backing with voice leading
Bass	2	Bass line with approach notes
Motif	3	Background pattern track (enabled by BackgroundMotif and SynthDriven)
Arpeggio	4	Synth arpeggios (when arpeggioEnabled: true)
Aux	5	Sub-melody support (pulse loops, groove accents)
Guitar	6	Accompaniment guitar (enabled by default)
Drums	9	Rhythm patterns with fills (GM drums)
SE	15	Section markers

Track Availability

Not all tracks are generated for every style:

• Motif track: Enabled in BackgroundMotif and SynthDriven; in MelodyLead, enabled only when the resolved paradigm, riff policy, addictive mode, or Blueprint section flow requests it. Section masks and layer schedules determine where notes remain
• Arpeggio track: Only when arpeggioEnabled: true (must be explicitly enabled, even in SynthDriven style)
• Guitar track: Enabled by default (guitarEnabled: true); set guitarEnabled: false to disable
• Vocal: Skipped with skipVocal: true; skipVocal does not skip Aux. SynthDriven disables both Vocal and Aux

For the complete eligibility rules, see Motif Generation Flow.

Next Steps

• Installation - Install the library
• JavaScript API - JavaScript/WASM API documentation
• C++ API - C++/C API documentation