Echo Nest has always appeared as a thing of deep magics to me. things like this tempt me to do crazy things with their API but then I am prevented by my lack of ANY knowledge of how music even works. Like, what would I do with the ability to time-stretch music? Probably make things sound like the Chipmunks and then forget about it. That's all I ever do with songs. By the way, Garth Brooks' The Thunder Rolls is hilarious at double speed.