While reading Elizabeth Hinkle-Turner’s book on women in electroacoustic music, I was reminded of Laurie Spiegel’s Music Mouse program. This is a mouse-driven generative music interface that Spiegel created all the way back in 1981. Spiegel used it to create a lot of her well-known pieces, including Appalachian Grove. Music mouse works basically by mapping the X and Y axes of the mouse position to diatonically-constrained pitches and harmonies.
Here’s a demo from YouTube. The fun stuff starts at 31 seconds.