Cute art and nice music!
Pretty much like the others have been saying, the background made it difficult to focus on the notes due to the lack of contrast. I found myself really distracted by the bouncing as well. Perhaps making the background bounce a little more subtly may help with that?
Making the notes disappear after hitting them would also help let us know when we hit a note or if we missed it.
Creating a rhythm game in the allotted time period seems difficult though so good job for what you got done. :)