Louis & Bébé Barron
The extraordinary thing for me about the soundtrack to the film Forbidden Planet (1956) by Bébé and Louis Barron was that, with 'living circuits', they completely avoided traditional notions of musical harmony (tonal or 12-note) and changed notions of what film music can be. They built beyond Arnold Schönberg's work.
I enjoyed and was influenced by Forbidden Planet, watching the ways that engaging with timbre for its own sake could enhance a film. Inevitably, the Barrons' sound worlds were linked with diegetic sound - which made composing a tricky act to balance! For me, it doesn't always work in Fred Wilcox's film, but when it does (e.g. in the Krell caves), boy does it work well.
Check out their music for the 1952 film Bells of Atlantis. It's such a shame the Barrons were not given the opportunity to work on further, bigger budget films. Their work on Forbidden Planet holds a key place in the history of electronic music for film.
Scenes from Fred Wilcox's Forbidden Planet (1956)