[gosub]

CoffeeCollider is a coffeescript clone of SuperCollider, it has a lot of options for subtractive/additive/fm/granular synthesis and algorithmic sequencing/composition.

http://mohayonao.github.io/CoffeeCollider/

[gecko39]

timbre.js (also from this person) is pretty cool too. http://mohayonao.github.io/timbre.js/

This weekend I used it to make a white noise generator for studying, etc.. http://www.noisemachine.co