Perhaps related: There's an app called "Shapes" on iTunes where the devs deconstructed popular songs into "shapes", basically a set of keys that will sound good

Perhaps related: There's an app called "Shapes" on iTunes where the devs deconstructed popular songs into "shapes", basically a set of keys that will sound good with the song no matter what you play: http://www.playshapes.com http://www.playshapes.com