Going back several decades, I always enjoyed the movies where James Mason played keyboard instruments. They were very candid in their shots, clearly showing his hands, body, and face all at the keyboard (not close edits to fake it) because he played the instruments well himself. Captain Nemo in Twenty Thousand Leagues Under the Sea and the older lothario in Georgie Girl are two that occur to me off the top of my head.

Robert Alda (father of Alan) is said to have practiced a great deal in order to play Gershwin in a biographical movie many years ago. I don't know if he did in fact play the music or just work that hard so he'd look like he was playing the music.

Then there is the subject of dubbing--Audrey Hepburn is widely thought to have lost the oscar when the news came out that Marnie Nixon dubbed her singing. They should have had Julie Andrews play the role anyway, it was hers on Broadway, but Hepburn was not bad as an actress in the role.

SRS