I thought it was really fun, though I'm not exactly sure how the jumping is supposed to work. I just spammed the button, and they would eventually jump.
Other than that, maybe you could add rocks or something to jump over.
The musical aspect was pretty cool. The ball hitting the pianos actually even made some decent melodies from time to time. The AI is pretty much impossible to win against, however. Unless you just don't move at the start, and then the game goes on forever. Overall, an interesting take on Pong, but it could use some polish.
I thought I was just going to play this game for a minute or so, and then move on, but I actually ended up spending about a half-hour beating it. It starts out really slow at first, but after you get some upgrades, it picks up and even becomes a bit addictive. Overall, surprisingly enjoyable! Maybe lower the cost of the upgrades at the start though, as the beginning was borderline infuriating with how slow it was.