WebGL and 3d graphics can be a powerful accompaniment to Web Audio enabling you to make rich audio/visual experiences. Three.js has already taken foot in the realm of interactive music videos. Here’s a few example:
Arcade Fire - Just A Reflector Lights - Ellie Goulding Three Dreams of Black - Danger Mouse & Daniele Luppi
Another WebGL library but focused entirely on 2d graphics. Good for mouse interaction (which is a little more difficult in Three.js), but with the faster rendering and added effects (shaders) of a WebGL.
Excellent for 2d graphics. Lots of examples and simple mental model (stateless) for drawing.
Two.js’ API is inspired by Three.js. It uses SVG instead of WebGL for rending. This makes it more widely supported than Three.js (though that’s becoming less and less true).
It excels at making blobs and smooth lines and is also easy to animate existing SVG graphics.
Examples:
Tether by Plaid Patatap - Jono Brandel