Jack Theakston wrote:Larry Fine was, of course, quite adept at the violin and you see him on-screen frequently with it.
Dick Powell supposedly could play every instrument in his band, but I don't know if he ever shows it off on-screen. Likewise, Fred MacMurray got his start with dance orchestras and played a number of instruments, and showed off on-screen a few times as I recall.
Jack Oakie played the piano a bit in a few early Paramounts. Also, Charley Chase with his banjo in a few Roach shorts. Also, too, Groucho and his guitar in Horse Feathers. I don't know if they were dubbed, but each looked as though they were playing although I didn't pay close attention (the quality of the Oakie Paramounts didn't allow close observation).
Jack Benny had MacMurray and Powell (also Dan Dailey, Tony Martin and Kirk Douglas) on one of his shows for a "jam session". If any was a virtuoso, they made sure not to show it.