Bernard Herrmann (1911-1975)
In his time, much film music was being composed in a late-Romantic style. In contemporary art music, things had moved forward. Bernard Herrmann brought modernist composition techniques to film.
I love all of his scores; in particular: The Day the Earth Stood Still (1951), Beneath the 12-Mile Reef (1953), Vertigo (1958), North By Northwest (1959), Psycho (1960), Torn Curtain (1966), Fahrenheit 451 (1966) and La mariée était en noir (1968) both directed by François Truffaut, who idolized him. Check out also his music for episodes of The Twilight Zone e.g. The Lonely (1959). Like its main character, his score to Martin Scorsese's Taxi Driver (1975-6) literally seethes with anger.
What I enjoy about Herrmann's style is the way he repeats and varies short musical cells (much like Stravinsky) with extreme economy. The way he orchestrates: often doubling large numbers of similar instruments, instead of doing the more expected thing of choosing different instruments to add. This is fascinating and economical in that two identical instruments playing together become more than the sum of their parts. I never forget one quote of his - that the music of the future would be very simple. In many ways, he was right.