so I've been reading about film scoring and how the composers typically use non-diatonic chord progressions (M3, m3 and tritone), for example C major to E-major and C major to E-flat major; to evoke certain emotions pretty consistently.
I really want to know how/why this works, and more importantly, if there is some system or framework that tells me how to compose with this in the context of an entire song because the song may have a lot of diatonic parts too. Basically, how does it all interact and fit together as a whole?
I am betting there's some classic books on this subject. I haven't read Schoenberg yet because I think that goes to one end of the extreme and presents 12-tone system, which is not what I'm looking for (I think).