Vexflow
A JavaScript library for rendering music notation and guitar tablature.
Wavesurfer.js
Navigable waveform built on Web Audio and Canvas
Tuna
An audio effects library for Web Audio, made by www.dinahmoe.com
Jsmediatags
Media Tags Reader (ID3, MP4, FLAC)
Web Audio Api
The Web Audio API, developed by the W3C Audio WG
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
Mp3.js
A JavaScript MP3 decoder for Aurora.js
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.
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.
Audio5js
The HTML5 Audio Compatibility Layer
Webaudio.js
web audio library for games
Audiolet
A JavaScript library for real-time audio synthesis and composition from within the browser
Howler.js
Javascript audio library for the modern web.
Flocking
Flocking - Creative audio synthesis for the Web
Midi Writer Js
♬ JavaScript library providing an API for programmatically generating expressive multi-track MIDI files in browser and Node.
Amplitudejs
A Javascript library that allows you to control the design of your media controls in your webpage -- not the browser. No dependencies (jQuery not required)