Dubious Historical Exercise

Composer Lawrence Dillon, over at Sequenza 21, is trying to determine, for pedagogical reasons I guess, what were the pieces of music from the 1960s, '70s, '80s, and '90s that most changed the way composers think about composing. I demurred offering my own choices, feeling a little out-of-mainstream in that milieu, and also having an innate proclivity for huge, long, relentless lists instead of brief, exclusive ones. He said, "Awww, c'mon!," which I found a sufficiently compelling argument for a lazy Sunday afternoon. It's an odd request as worded, because those pieces from the '60s formed my conception of music, those from the '70s changed it, but by the '90s, very little was really going to change the way I compose - though I'll admit, Mikel Rouse's Failing Kansas did. Anyway, for what it's worth, here's my personal list for Lawrence, as short as I dare make it, and posted on my own blog so I can add important things I forgot:

1960s:
Pierre Boulez: Pli selon pli (1962)
Terry Riley: In C (1964)
Igor Stravinsky: Requiem Canticles
Harry Partch: The Delusion of the Fury (1965-66)
John Cage: Variations IV (1963)
Luciano Berio: Sinfonia (1967)
Henri Pousseur: Jeu de Miroir de Votre Faust (1968)
Bruno Maderna: Grande Aulodia (1969)
Philip Glass: Music in Fifths (1969)

1970s:
George Crumb: Black Angels (1970 - no big impact on me, ultimately, but still wows my students)
Karlheinz Stockhausen: Mantra (1970)
Tom Johnson: An Hour for Piano (1971)
Morton Feldman: Rothko Chapel (1972)
Frederic Rzewski: Coming Together (1972)
Ben Johnston: String Quartet No. 4, "Amazing Grace" (1973)
Steve Reich: Music for Mallet instruments, Voices, and Organ (1973)
Philip Glass: Einstein on the Beach (1976)
Morton Feldman: Why Patterns? (1978)
Robert Ashley: Perfect Lives (1978)
William Duckworth: The Time Curve Preludes (1978-79)

1980s:
Harold Budd/Brian Eno: The Plateaux of Mirror (1980)
Morton Feldman: For Philip Guston (1984)
Conlon Nancarrow: Studies Nos. 40, 41, 47, 48 (1980s)
Daniel Lentz: The Crack in the Bell (1986)
Janice Giteck: Om Shanti (1986)
Carl Stone: Shing Kee (1986)
Morton Feldman: For Samuel Beckett (1987)
La Monte Young: The Well-Tuned Piano (begun in 1964, but perhaps not totally impressive until the 1981 and 1987 performances)
Larry Polansky: Lonesome Road: The Crawford Variations (1988-89)
Bunita Marcus: Adam and Eve (1989)
Art Jarvinen: Murphy-Nights (1989)

1990s:
Meredith Monk: Atlas (1991)
Frederic Rzewski: De Profundis (1991)
David First: Jade Screen Test Dreams of Renting Wings (1993)
Mikel Rouse: Failing Kansas (1995)
Mikel Rouse: Dennis Cleveland (1996)
John Luther Adams: In the White Silence (1998, or alternatively the piece it's expanded from, Dream in White on White, 1992)
Elodie Lauten: Waking in New York (1999)

There should be pieces by Phill Niblock, Beth Anderson, and Peter Garland, but it's difficult to narrow it down to one.