Also, you went from:
"Beethoven, Mozart, Berlioz, Liszt, Wagner etc are all innovative original and experimental artist, ahead of it's time and some cases even subversive. The have been descreibed as "avantgarde" by Prof Robert Greenberg due to this (which I disagree with)"
"Mozart is avantgarde because his opera was original in creating continuous dramatic motion in his music. His opera's was subversive as Marriage of Figaro is essentially class warfare at the aristocracy and mocked the very group of people who funded and paid for his career and Cosi Fan Tutti was considered immoral, sexist, raunchy and vulgar opera back in the day. However apart from people using avantgarde as an adjective (avantgarde like work due to it's originality) he is never classified as an avantgarde artist "
You already said Greenburg considers Mozart avant-garde, then said that no one considers Mozart avant-garde.
Also, Good Vibrations is widely regarded as an avant-garde work, so again, you're trying to change the idea of what avant-garde work is:
"Mike Love submitted the final lyrics for "Good Vibrations", claiming to have written them on the drive to the studio. Love reacted upon hearing the unfinished backing track: "[It] was already so avant-garde, especially with the theremin, I wondered how our fans were going to relate to it. How's this going to go over in the Midwest or Birmingham? It was such a departure from 'Surfin' U.S.A.' or 'Help Me, Rhonda'.""
"three minutes and thirty-six seconds of avant-garde pop".
"masterpiece of avant-pop".
Also from wikipedia: https://en.wikipedia.org/wiki/Avant-pop
"Avant-pop is popular music that is experimental, new, and distinct from previous styles while retaining an immediate accessibility for the listener.
Generally, "avant-garde music" refers to music which attempts to challenge or alienate its audiences by being purposely outrageous, whereas "popular music" is designed to have mass appeal. Writer Tejumola Olaniyan describes "avant-pop music" as trangressing "the boundaries of established styles, the meanings those styles reference, and the social norms they support or imply." Paul Grimstad says it's music that "re-sequences the Legos of song structure, so that (a) none of the charm of the tune is lost, but (b) this very accessibility leads one to bump into weirder elements welded into the design." The Tribeca New Music Festival defines it as "music that draws its energy from both popular music and classical forms", and that it ranges from Charles Ives to Frank Zappa."