One day, I realized that when I played scale passages on the piano, they were uneven, and that part of the problem was that I couldn’t always tell how unevenly I was playing. So I made a tool that represented each note as a block of color, with the height of the block showing the loudness, and the width showing the timing.

This allowed me to see how much notes overlapped and how loud they were. (It didn’t improve my playing, much, though.)