An HTML5 web audio API hack built for Music Hack Day SF 2012
You can play with a hosted version found here: http://forgan.herokuapp.com
It uses the Echonest API to retrieve metadata about a song and attempts to recreate the song using in-browser audio synthesis. The Echonest audio summary data contains segments that describe discrete portions of the song, such as duration and a pitch vector.
That information is used to compute an approximate representation of the song (very approximate).
It was built over a span of about 24 hours (the lion's share of it), so please excuse the messiness. I plan on cleaning things up down the road.
It still needs work to sound more like the source material, but I think it's pretty cool.