Although it can be proven that there are exceptions to the rule, a commonly accepted generality about the Academy is that its music branch is a highly insular clique, showing a persistent preference to established mainstays and often avoiding artists who don't work explicitly in the realms of film and television. But despite the fact that the music branch shies away from such composers, many filmmakers have welcomed their refreshing outsider take on movie music, especially so in the last decade. I thought I'd give a shout out to some of the finest film scores (yes, I'm including song scores as well) from musicians whose notoriety primarily stems from outside the relatively narrow niche of film scorers.
(Interesting side note: The Golden Globes are much more receptive to outsider musicians than AMPAS, having bestowed nine nominations upon the following ten scores compared to the Academy's two.)