Awesome project! As a professional audio developer, I was really blown away that this was the author's first project working with audio.

For anyone interested, I'd recommend checking out "The Infinite Jukebox", which has a similar goal, but perhaps a more robust approach: http://infinitejukebox.playlistmachinery.com

If I had to guess at why your approach didn't work well on recorded music, it's probably because most of the time, there is more than a single event happening at a time, so picking out just the highest FFT bin is probably not a very robust "fingerprint" of that part of the music. The infinite jukebox uses timbral features as the fingerprint, rather than just a single note.