I’m trying to make a list of films with hummable themes that are not only heard on the soundtrack but sung or played by characters within the narrative. Like John Williams‘ theme for The Long Goodbye. It’s on the soundtrack, of course, but there’s also a bit in a bar in which some guy is trying to learn how to play it on the piano. We also hear it on a supermarket’s loundspeaker system. Leonard Rosenman‘s theme for East of Eden is hummed by Julie Harris and Richard Davalos. Musical scores are typically composed after principal photography and usually after the first initial edit. I just can’t think of other examples.