Tone.js
A Web Audio framework for making interactive music in the browser.
Audiolet
A JavaScript library for real-time audio synthesis and composition from within the browser
Audio5js
The HTML5 Audio Compatibility Layer
Audio.js
A cross-browser javascript wrapper for the html5 audio tag
Waud
Web Audio Library
Sound Manager 2
A JavaScript Sound API supporting MP3, MPEG4 and HTML5 audio + (experimental) RTMP, providing reliable cross-browser/platform audio control in as little as 10 KB. BSD licensed.
Web Audio Api
The Web Audio API, developed by the W3C Audio WG
Alpha Tab
alphaTab is a cross platform music notation and guitar tablature rendering library.
Mp3.js
A JavaScript MP3 decoder for Aurora.js
Flac.js
FLAC decoder in JavaScript
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)