Web Audio Sequencer

Web Audio Sequencer is a library for writing music on the web in a declarative style. It abstracts away the complexity of the Web Audio API and lets you make music by simply describing what it should sound like.

Things the library handles for you

• Creating and connecting Audio Nodes such as oscillators, filters, and amps.
• Automating envelopes
• Scheduling notes to play at the correct time
• Looping

Example Usage

Install the package:

npm i web-audio-sequencer

Create an object that describes your music:

import { Sequencer, AudioState } from "web-audio-sequencer"
...
const state: AudioState = {
  bpm: 120,
  bars: 1,
  sequences: [
    {
      synth: {
        shape: "sawtooth",
        filter: { q: 2, frequency: 10000 },
        envelope: { attack: 0.03, sustain: 0.1, release: 0.1 },
      },
      notes: [130, 196, 174, 155, 196, 233, 196, 261],
    },
    {
      synth: {
        shape: "square",
        filter: { q: 2, frequency: 10000 },
        envelope: { attack: 0, sustain: 0.1, release: 0.1 },
      },
      notes: [130, 233],
    },
  ],
  loop: true,
};

Then create a sequence from your object:

const seq = Sequencer(state);

Now you can start, pause and resume your sequence:

seq.start();
seq.pause();
seq.resume();

You can update your sequence while it is playing. Your updates will reflect in the next loop. To update your sequence, just pass a new state (or a partial new state):

seq.update({bpm: 110})

That's it!

Roadmap

This library is a work in progress and not ready to be released on NPM yet. Remaining work includes:

• ~~Updating the sequencer state in place~~
• Assigning a relative gain to oscillators dependent upon the total number of sequences
• Supporting note names in sequences, rather than just frequencies