Now that you mention this, I do remember reading some years ago about a machine-learning composition project that had the algorithm generate random streams and learn what music people liked by crowd-sourcing feedback.

I think what you've described is a great idea, and I would pay for it.

Ideally, it would let me have different-styled streams dependent on what I want to do with the music / what activity I'm doing while listening. Triple bonus points if it can consume an existing piece of music to learn more about some particular style of stream that I want.