Whoa! It's a democratic poll, and my opinion, with its incredibly tenuous expertise, is being treated as equal to those of you who are classical-music mavens! Cool! As the milieu of classical composition has diversified, it seems reasonable to me (who knows not a ton, and may not be best informed) to expand the criteria for "distinguished" master composer. I'm behind Ligeti and Zappa's admission (in the long run, Zappa's probably done for classical what the seminal incorporation of jazz-influences did before). I would add Gavin Bryars (1943) because I think that what he's created is not merely popular but important. But most of all, for anyone who has voiced a vote for John Williams, I'd counter with two votes for Ennio Morricone (1928).