Hi…
Well the 60's saw a confluence of the avant-garde in two threads.. 'modern' classical and Jazz.. Cecil Taylor, Albert Ayler, continuing with H. Threadgill (who I like a lot…"too much ammonia" there was 'musique concrete' , electronic experiments (Subtonik being a great example), minimalism , starting with Riley's 'in C' , cont'd with Reich, Glass, Adams.. and scores of others in varying degrees...*(Adams has done a wonderful suite of piano pieces call 'Phrygian Gates' - .. a great contribution, considering that the piano has lost it's center stage status it once had with composers..) a continuing of the complexity started by Schoenberg, which was further explored.. (Boulez, E. Carter -whose string quartets are fantastic) Ferneyhough, Babbitt, Stockhausen, many others… There is 'space' music (like in empty) like Eno's 'thursday afternoon', … Toro Takemitzu …. Oh I should throw in there the incredible Etudes for Piano of Ligeti … Also of course, the chance music of Cage, Feldman, ...Carl Stone's electronic experiments with the electronic surreal. Then the return to and refashioning of older forms - Arvo Part, Golijov , Alan Silvestri… And those who push the bounds in film music… John Corigliano - "Altered States"….
(Also, somewhere in there was this mov't of "The return of melody"… in the late 70's)