whoops. Minute waltz is what I ment. Anyway, the cartoon I was talking about was called 'sparky's magic piano'. I found a synopsis on the net, it sounds like the one:
"An eight-year-old boy who hates to practice the piano, one day realizes his piano is magic and soon, to the amazement of all, he is a "gifted" virtuoso. But soon Sparky's success goes to his head."