Originally posted by Diki:
Film MUSIC is copyright, but the arrangement? There's a long history of taking hit music, or film scoring styles, and applying them to new music, and no-one gets sued...
You can't copyright a beat, or a way of voicing the strings, etc.. Only the music itself has protection, AFAIK.
Anyone remember when John Fogerty got sued for plagiarizing HIMSELF..??!!
Some record company owned the old CCR back catalog, and sued him (I think it was for 'Old Man Down the Road', but not sure) for writing something similar to what he had already written!
You gotta love lawyers! 
You are right if I IV V progressions and I VIm IIm V could only be used in one song each. 100,000 songs would have never hit the airwaves. 12 tones does not lend to a whole lot of originality.