The music is wonderful, and the puzzles are quite challenging! I had a great time working through each one. Puzzle 14 was by far the hardest, but funnily enough, I completed it in 24 moves (gold was 26) which means my level is still highlighted blue :P.
My only comment would be that I wish there was a way to fullscreen the game. It was really small on my monitor which actually made me miss that TAB lets you choose the note to move. You can imagine my frustration at level 9 xD, but I eventually checked out the tutorial again and saw my error... whoops!