Music has the ability to tell a story through abstraction. It can lend context to content. This is what drives the purpose of underscore. The composer helps the director tell the story without words, or even, for that matter, picture. The story is told, the audience is made the wiser, and the emotional impact of the scene, the dialogue, the character arc, the film as a whole, is enhanced.

This is what fascinates me so about film music, and music in support of other media in general, be it television or video games. This is the very thing that drives me. The ability of music to be a story teller.