Well. Quite a few.
I watched The Talented Mr Ripley again on the weekend, and music is really central to the movie. Ripley plays classical pieces on any grand piano he can get his hands on, as well as being compelled to take an interest in jazz piano. Anyway, I'm sure it's Matt Damon playing (parts of) many of the pieces in the movie, two or three times I spotted his name as the performer in the credits. An imdb.com trivia spot says that Damon learnt to play for the film.