When I write the script, I hear the movie more in terms of the music than I do in terms of sound effects. I can actually hear it in my mind. I pay a lot of attention to the music, even during the early stages of writing. The Star Wars movies are, in essence, silent movies because they are stories that are told visually; and in silent movies the relationship between image and music is everything. A lot of the story and a lot of emotion are told through the music. It is one of the most important elements of a film.
George Lucas, The Making of Episode I – The Phantom Menace