meSing.js : 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...
Bliss.js : Want to use Vanilla JS but find native APIs a bit unwieldy? Bliss is for you
jsfx : This is a javascript library (with frontend) for sound effect generation.
SoundManager 2 : Using HTML5 and Flash, SoundManager 2 provides reliable cross-platform audio under a single JavaScript API.
Wave.js : Audio visualizer library for javascript. Create dynamic animations that react to an audio file or audio stream.
Fast, JavaScript DSP library that creates JIT optimized audio callbacks using code generation techniques.
It is designed to be a fast audio API for browser based audio content.