moont-web

WebAssembly wrapper for the moont CM-32L synthesizer. Provides a Cm32lSynth struct that hooks into the Web Audio API via ScriptProcessorNode for real-time audio output at 32 kHz.

Usage from JavaScript

Build with wasm-bindgen --target web:

import init, { Cm32lSynth } from './moont_web.js';

await init();
const synth = new Cm32lSynth();  // requires bundle-rom feature

// Note On: MIDI channel 2, note C4, velocity 100.
synth.play_midi(new Uint8Array([0x91, 60, 100]));

// Note Off: MIDI channel 2.
synth.play_midi(new Uint8Array([0x81, 60, 0]));

Without the bundle-rom feature, load ROMs dynamically:

const ctrl = new Uint8Array(await fetch('CM32L_CONTROL.ROM').then(r => r.arrayBuffer()));
const pcm = new Uint8Array(await fetch('CM32L_PCM.ROM').then(r => r.arrayBuffer()));
const synth = Cm32lSynth.from_rom(ctrl, pcm);

Features

bundle-rom — Bundles the CM-32L ROMs into the WASM binary, enabling the new Cm32lSynth() constructor. Enables moont/bundle-rom.

Building

cargo build -p moont-web --target wasm32-unknown-unknown --release --features bundle-rom
wasm-bindgen --target web --out-dir pkg target/wasm32-unknown-unknown/release/moont_web.wasm

A demo/ directory and tools/run-web-demo.sh script are included in the repository for quick local testing.

Related Crates

Crate	Description
moont	Core CM-32L synthesizer library
moont-render	Render .mid files to .wav
moont-live	Real-time ALSA MIDI sink

License

moont-web is distributed under LGPL 2.1+.

Copyright (C) 2021-2026 Geoff Hill geoff@geoffhill.org