American composer Aaron Copland on the role of film music:

I was very fascinated by the medium because a composer can be a real help in the making of a film. The way you can prove that, of course, is to see a film before the public has seen it, in the studio room, and imagine what the music might be like that would accompany a particular scene. It might be a love scene and you think that if you add music to that it would seem even more touching and more emotional. And then, of course, you go away and you write the music ― not very far away, just round the corner on the lot ― and they bring in a symphony orchestra for you and we record the music. And then you have the great pleasure, and a rather nervous one in the beginning, of hearing your music played while that same scene is put on the screen. You’d be amazed at what music does to an emotional scene that you’re really interested in. The audience may not even know that there’s music going on. The easiest thing in Hollywood is to turn the music off so you can watch the scene without the music, then add your music and take the music away. And you’ll see how much more human, how much more touching, how much more emotional the whole thing seems to feel, even though the audience doesn’t even realise that music is being played in the theatre. They are so absorbed in the drama of it all ― and that’s the way it should be really, except for musicians. You see, musicians can’t ignore music and they know when the music is turned down right away. It might even get into their way because they’re so aware of it. So it could be a hindrance to a musician. But to the general public ― I don’t think they are sufficiently aware of what music does to make the cold screen more warmly human. More feelingful or more exciting. I mean in battle scenes, for instance. Whoever heard of an orchestra in a battle? You wouldn’t know the music was there. It just helps make everything more exciting and hectic etc.

Cited in: Dickinson, Peter (ed.) (2002) Copland Connotations: Studies and Interviews. Rochester: Boydell Press, p. 189.