Bartok and Messiaen are probably the next ones to check out after Stravinsky. In terms of harmoic/rhythmic sophistication, Messiaen still sounds as modern to me

Bartok and Messiaen are probably the next ones to check out after Stravinsky. In terms of harmoic/rhythmic sophistication, Messiaen still sounds as modern to me as the recent/current orchestral composers (Adams, Carter, etc).