Wavesurfer.js
Navigable waveform built on Web Audio and Canvas
Vexflow
A JavaScript library for rendering music notation and guitar tablature.
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.
Speak.js
Text-to-Speech in JavaScript using eSpeak
Jsmediatags
Media Tags Reader (ID3, MP4, FLAC)
Alpha Tab
alphaTab is a cross platform music notation and guitar tablature rendering library.
Pizzicato
Library to simplify the way you create and manipulate sounds with the Web Audio API.
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
Audio.js
A cross-browser javascript wrapper for the html5 audio tag
Teoria
A JavaScript music theory framework.
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.
Midi Writer Js
♬ JavaScript library providing an API for programmatically generating expressive multi-track MIDI files in browser and Node.
Pedalboard.js
Open source JavaScript framework for developing audio effects for guitars using the Web Audio API.
Mp3.js
A JavaScript MP3 decoder for Aurora.js
Audio5js
The HTML5 Audio Compatibility Layer
Howler.js
Javascript audio library for the modern web.