The Web Audio API, developed by the W3C Audio WG
Web Audio DAW. Use the HTML5 Web Audio API for dynamic sound synthesis. It's like jQuery for your ears.
alphaTab is a cross platform music notation and guitar tablature rendering library.
Navigable waveform built on Web Audio and Canvas
The HTML5 Audio Compatibility Layer
Flocking - Creative audio synthesis for the Web
web audio library for games
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.