The old movies aren't always the best, but frequently they beat hell out of most of what Hollywood has to offer today. Consider the Warner Bros. classic, Deception, from 1946 starring the powerhouse trio of Bette Davis, Claude Rains and Paul Heinreid. He is a virtuoso cellist, Rains is an imperious composer of world-class stature and she is the love interest of both.
Now, apart from the dramatic intensity these three bring to the picture, what struck me was Heinreid's masterful faux-playing. It is unfailing that actors called upon to play instruments do so amateurishly, with halting, spastic movements -- if they even bother to move at all.
He bows and fingers like Yo-Yo Ma, perspiration glistening on his forehead, deep in concentration. Really quite astounding. And it's critical, since the role requires him to be shown playing lengthy passages.
Since writing the above, I came across a this IMDB thread. Somehow, I hope it's not true.