One of the highest rated album in Classical Music, all genres, is Steve Reich's Music for 18 Musicians released in 1978. The genre is called Minimalism, which is a branch of Modern Classical. Minimalism has connections to electronic and experimental music as well (initiated by Terry Riley back in the late sixties). I'm not necessarily crazy about minimalism but looking for the most immediately striking stuff of the kind, I must say that Gavin Bryars The Sinking of the Titanic from 1975 is a piece of beauty. Here the minimalism is much less radical and actually closer to Classical Music. I must have heard this thing already but can't remember where or when. Maybe in a movie.