Goshu

So, an older Ghibli movie that is hard to find. But it's really good, especially for musicians.
Gauche the cellist the cellist (though his name is actually Goshu...)
Anyway, it's about Goshu, a cellist. Can you tell? He's in a professional band, but he's sort of the worst player in the band. Over the course of the movie, he slowly learns more about music from a series of strange visitors. At first he is very mean to these "teachers" but his attitude improves along with his playing. It's a great movie.