Wavesurfer.js
Navigable waveform built on Web Audio and Canvas
Vexflow
A JavaScript library for rendering music notation and guitar tablature.
Jsmediatags
Media Tags Reader (ID3, MP4, FLAC)
Web Audio Api
The Web Audio API, developed by the W3C Audio WG
Tuna
An audio effects library for Web Audio, made by www.dinahmoe.com
Midi.js
Making life easy to create a MIDI-app on the web. Includes a library to program synesthesia into your app for memory recognition or for creating trippy effects. Convert soundfonts for Guitar, Bass, Drums, ect. into code that can be read by the browser. Supports multiple simultaneous instruments and perfect timing.
Mp3.js
A JavaScript MP3 decoder for Aurora.js
Pedalboard.js
Open source JavaScript framework for developing audio effects for guitars using the Web Audio API.
Audio.js
A cross-browser javascript wrapper for the html5 audio tag
Audio5js
The HTML5 Audio Compatibility Layer
Midi Writer Js
♬ JavaScript library providing an API for programmatically generating expressive multi-track MIDI files in browser and Node.
Audiolet
A JavaScript library for real-time audio synthesis and composition from within the browser
Webaudio.js
web audio library for games
Buzz
Buzz is a small but powerful Javascript library that allows you to easily take advantage of the new HTML5 audio element. It tries to degrade gracefully on non-modern browsers.
Timbre.js
JavaScript library for objective sound programming
Flocking
Flocking - Creative audio synthesis for the Web
Flac.js
FLAC decoder in JavaScript