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...
howler.js : howler.js is an audio library for the modern web. It defaults to Web Audio API and falls back to HTML5 Audio.
SoundManager 2 : Using HTML5 and Flash, SoundManager 2 provides reliable cross-platform audio under a single JavaScript API.
jsmad : jsmad is a pure javascript MP3 decoder, based on libmad, with an ID3 decoder written from scratch.
jsfx : This is a javascript library (with frontend) for sound effect generation.
The Javascript Sound Kit is a wrapper around the ActionScript Sound Object, it makes it possible to use the Sound Object in Javascript the same way you do it in ActionScript.