anyone know what the music is...

It's part of the soundtrack, specially written for this film.

I'm not sure if this will help at all, but the composer of the score is Toru Takemitsu. He's composed many great scores for many great films

The track title is "Hell's Picture Scroll", and was apparently modeled after the final movement of Mahler's Das Lied von Erde (The Song of the Earth). Kurosawa was using this piece as a temp score and pressed Takemitsu to write a piece in a similar vein, which nearly lead to a rift between the director and the composer, with Takemitsu threatening to quit. Takemitsu ultimately acceding to Kurosawa's demands to composer a Mahlerian piece, albeit reluctantly.

"Hell's Picture Scroll" from the Ran soundtrack by Takemitsu:
https://www.youtube.com/watch?v=pWqih7FCbjQ

"Der Abscheid" (The Farewell) from "The Song of the Earth" by Mahler:
https://youtu.be/69fZ-s-NCHQ