RTTTL Web Audio Synth

This started as a fun side project more than 10 years ago, originally used to add a few sound effects to websites. Now it has been revived into a complete TypeScript library with AI assistance, plus a modern Playground that includes a huge built-in RTTTL preset library ready to copy and play. Not sure if anyone will use this project, but I'll publish it just for fun.

Screenshot

Install

npm i web-rtttl-synth

Quick Start (Facade API)

import {playRTTTL} from 'web-rtttl-synth';

const handle = await playRTTTL('Tune:d=4,o=5,b=160:c,e,g,c6', {
    oscillatorType: 'square',
    onStart: ({ bpm, noteCount }) => console.log('start', bpm, noteCount),
    onStop: ({ reason }) => console.log('stopped', reason),
    onEnded: ({ playedCount, totalNotes }) => console.log('done', playedCount, totalNotes),
});

// stop early if needed
handle.stop();

Controller API (Advanced)

import {createSynth} from 'web-rtttl-synth';

const synth = createSynth();
synth.loadRTTTL('Nokia:d=4,o=5,b=180:e,d,f#,g#', {bpmOverride: 180});

const handle = await synth.play({
    oscillatorType: 'triangle',
    onNoteStart: ({ index, playedCount, remainingCount }) => console.log('note start', index, playedCount, remainingCount),
    onNoteEnd: ({ index, playedCount }) => console.log('note end', index, playedCount),
});

await handle.whenEnded;
synth.dispose();

Utility APIs

• parseRTTTL(text) returns parsed note events.
• extractRTTTLBpm(text) returns the RTTTL b= value or null.
• buildPlaybackTimeline(notes, bpm) returns deterministic schedule points in seconds.
• warmupAudio() pre-warms shared audio context to reduce first-play latency.

import {warmupAudio} from 'web-rtttl-synth';

document.addEventListener('pointerdown', () => {
    void warmupAudio();
}, {once: true});

Options

• oscillatorType: 'sine' | 'square' | 'sawtooth' | 'triangle' | 'noise'
• bpmOverride: force BPM instead of RTTTL default.
• envelope: { attackSeconds, releaseSeconds, peakGain }
• callbacks: onStart, onStop, onNoteStart, onNoteEnd, onEnded

Browser Notes

• Requires a browser environment with AudioContext.
• Playback must be triggered from user interaction in most browsers.

Local Development

npm install
npm run dev        # playground app
npm run build:lib  # ESM + CJS + .d.ts outputs
npm test

Credits

Some preset collections in the Playground were curated and adapted from these community resources:

• RTTTL parsing reference and inspiration: https://1j01.github.io/rtttl.js/
• Public ringtone browsing source: https://ringtone.vulc.in/
• Large ringtone text dataset source: https://microblocks.fun/mbtest/NokringTunes.txt