Thanks for your thoughtful comment, Justin. My argument is based on the fact that most, if not all Western art forms have been demolished during the last century. Visual art got dismantled, starting from impressionists in the latter part of 19th century, followed by expressionists, then fauvists, cubists, etc. all the way to abstract art and then empty white canvases hanging in museums. Dead, deceased, is no more.
Literature too, starting with Joyce etc. Classical music — twelve tone, atonal (Shoenberg) etc. all the way to Stockhausen and John Cage’s 4 and a half minutes of silence. Dead, deceased, is no more.
The only refuge of ‘regular’, or ‘normal’ music (i.e. music with melody, harmony, regular, predictable beat, etc.) was popular music. The first form of popular music that got dismantled was jazz — you mentioned free jazz that gutted the traditional jazz in the late 1950’s — early 1960s. Next came the non-instrumental popular music — the Beatles dismantled it with “A Day In The Life”, and then hit the last nail in its coffin with “Revolution 9”. After that, all that was left for popular non-instrumental music is to resort back to derivative forms, trying to resuscitate the genre by reaching back into the past. But no innovation ever occurred after 1968, just regurgitation of the same old. Dead, deceased, is no more.
So, that leaves us with popular instrumental music (i.e. non-classical, which was by that time already dead as a doornail). Miles Davis took the cue from Stockhausen and the Beatles and heroically went in to single handedly dismantle what was left of instrumental music (rock, funk, soul, etc.) Pay attention to how Miles made doubly sure that everyone knows how he was not into jazz at that point. Miles abandoned jazz sometime in 1968, turned his back to it (and never looked back). He now went into funk etc. with a vengeance.
Davis’s dismantling of instrumental music became very evident by 1972, when he released his seminal “On The Corner” album. Music on there is verging on non-sensical. Later on, Miles would elaborate even further by releasing long tracks that were based on utmost monotony (“He Loved Him Madly” from “Get Up With It” and “Rated X” from the same album). But it was during his live performances where he managed to put the last nail in the coffin of instrumental music.
After 1975, instrumental music had only one place to go — elevator music, soft jazz, muzak. Some attempts were made to resuscitate popular music by creating a fusion with so-called ‘world music’, but to little effect. Gone was the innovation, the daring playfulness with the form.
Today, the only form of music that remains untouched is the spoken word music (rap, hip hop).