Once the Music Animation Machine was operational, it was obvious how much was missing from it: you couldn't tell anything about timbre, very little about harmony, not much about rhythm... So I started trying to figure out how to enhance the display. The first thing I experimented with was tonality, as based on the "perfect fifth."   The idea was that the colors in the artist's "color wheel" could be applied to notes in a way that showed what was going on in the harmony. (More about this here.)