There are few things more powerful than the perfect combination of music and visuals. Think of your favorite movie scenes, and I’d be willing to bet they’ve got amazing music in them.
On one hand, you’ve got the great film composers; Herrmann, Goldsmith, Williams, and so on. They’re all worth study in their own right, of course. But what I find equally powerful, and arguably more interesting, is the effective use of popular music.
Interesting, because often, directors (and presumably, music supervisors) get it so horribly wrong.