Band.js : An interface for the Web Audio API that supports rhythms, multiple instruments, repeating sections, and complex time signatures.
Essentia : Open-source library and tools for audio and music analysis, description and synthesis
SoundManager 2 : Using HTML5 and Flash, SoundManager 2 provides reliable cross-platform audio under a single JavaScript API.
meSpeak.js : meSpeak.js (modulary enhanced speak.js) is a 100% client-side JavaScript text-to-speech library
howler.js : howler.js is an audio library for the modern web. It defaults to Web Audio API and falls back to HTML5 Audio. This makes working with audio in JavaScr...
meSing.js is a JavaScript singing synthesis library that uses the Web Audio API's DSP capabilities in conjunction with the meSpeak.js speech synthesis library to provide a vocal synthesizer for the web.