From Music Hack Day
Miguel Senquiz - User Experience, Project cheerLEAD, Beat Battle build (php/soundcloud api)
 About the hack
DISCLAIMER: This project was started at the Visual Music Masterclass @ Eyebeam in July 2010.
Basic idea was to see how far we could go with HTML5 audio and JS.
Official #musichackday additions are export wav/mp3/ogg to Soundcloud, and a hot-or-not-ish competition called "PatternSketch Beat Battle" comparing two patterns created with Patternsketch, leaderboard, etc.
 What APIs, tools or kit did you use?