on beauty in dissonant 20th Century (classical) music

In reply to my FB post about watching the BBC Prom 2010 of Rattle conducting 3 works by Schoenberg, Webern, and Berg from their atonal period (1911-1920), and asking rhetorically again why I love that music, someone replied,

There really are some good (albeit mostly neoclassical) composers in the 20th century - Vaughn-Williams, Thompson, Copeland, Gershwin (that's about one every twenty-five years on average, but none of them worked much after 1950). the fact of the matter is that much 20th century music was "experimental" and like most experiments, it failed. I particularly remember one experimental piece that had breaking glass as the solo "instrument."

( Needless to say, this got me started... )