Wave.js : Audio visualizer library for javascript. Create dynamic animations that react to an audio file or audio stream.
jsfx : This is a javascript library (with frontend) for sound effect generation.
RAWGraphs : RAW is an open web tool to create custom vector-based visualizations on top of the amazing d3.js library.
Primarily conceived as a tool for designers ...
jsmad : jsmad is a pure javascript MP3 decoder, based on libmad, with an ID3 decoder written from scratch.
howler.js : howler.js is an audio library for the modern web. It defaults to Web Audio API and falls back to HTML5 Audio.
dancer.js is a high-level audio API, usable with both Mozilla's Audio Data API and Webkit's Web Audio API with flash fallback, designed to make sweet visualizations.