Otomata is a project mainly written in JavaScript, it's free.
Otomata music generator made in HTML5 using canvas
Otomata in HTML5 demo is based on the awesome flash music generator by Batuhan Bozkurt. Method was reversed engineered and ported into canvas with HTML5 audio support.
I release only the JS source of the demo, as you can easily deploy it to a page using HTML5 Boilerplate template by Paul Irish or you can just create a page with a div id="main" in it to host the game.