I actually noticed the word "yank" in your first post, and thought it was an odd choice of words, but somehow I never put two and two together. I should know better by now!
Jimmy Cagney:
Real-life Naval Commander - The Gallant Hours (as Bull Halsey)
Fictional Naval Officer - Mister Roberts (tie-in to William Powell)
Real-life actor - Man of a Thousand Faces (as Lon Chaney)
Real-life composer - Yankee Doodle Dandy and The Seven Little Foys (as George M. Cohan)
"Composer" is a perfectly good word for George M. Cohan. It crossed my mind to wonder if you meant a classical composer or a popular songwriter, but I don't think it would have helped if I had known the answer.