What are some alternatives?
SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).
Splice Beat Maker - Make and share beats in your browser
Ramsophone - A generative art/music machine. (Be sure to refresh!)
Airdog 2 - All-terrain, camera drone that follows you in action
Cycle - (taken from the man pages) DESCRIPTION
Google Music Lab - Interactive experiments that use the Web Audio API