That was cute.
Not too shabby for the time constraint you had.
At first I was confused as to what to do, but it wasn't too hard to figure out. I was entertained when I solved that last puzzle. I liked that all the music puzzles came together. Then i made the happy ghost girl dance for a few seconds. It made me smile and for that alone was worth playing it.
This would be fun as a kid's first steps into puzzle solving and perhaps music.
Cheers!