Several books have tackled the question of film music's purpose, and there has been a good variety of answers. Here are some I'd recommend in addition to Shark's excellent suggestions: - Royal S. Brown, Overtones and Undertones - Claudia Gorbman, Unheard Melodies - Peter Larsen, Film Music - Kathryn Kalinak, Settling the Score - The Hollywood Film Music Reader - The Routledge Film Music Sourcebook The last two have particularly good and well-known quotations from Bernard Herrmann and Aaron Copland, which may be helpful.