Really cool game idea!
Don't know why, but it took me a while to figure out that you can slide things (spent a couple of minutes in level 2).
I did found it a little jarring that when you finish the puzzle you still get the breaks in the song. It would probably be very complicated to do levels that match the travel distances between puzzle elements and time those with backround music so that when you complete the puzzle you get the same starting "phrase", but that would make it really awesome!