Does anyone know if Aristotle wrote anything on music, and if so what was it and where can I find it?

Yes - in The Politics. I believe he thought that it was character-forming, and so should form part of the education of the young. Plato, IIRC, thought that it encouraged unhealthy emotions, and so had no place in a well run state (see The Republic).

Are you sure you don't want Pythagoras?

Thank you but I know which Philosopher I'm after and I am familiar with Pythagoras.

Never does to be TOO familiar with a numerologist!