Stanley Kubrick on Film Music

"Unless you want a pop score, I don't see any reason not to avail yourself of the great orchestral music of the past and present. This music may be used in its correct form or synthesized, as was done with the Beethoven for some scenes in A Clockwork Orange. But there doesn't seem to be much point in hiring a composer who, however good he may be, is not a Mozart or a Beethoven, when you have such a vast choice of existing orchestral music which includes contemporary and avant-garde work. Doing it this way gives you the opportunity to experiment with the music early in the editing phase, and in some instances to cut the scene to the music. This is not something you can easily do in the normal sequence of events."
—Stanley Kubrick in an interview with Michel Ciment