Cage and the Avant-Garde

[Floristan]

If you develop an ear for sounds that are musical it is like developing an ego. You begin to refuse sounds that are not musical and that way cut yourself off from a good deal of experience.
  - John Cage

I found this quote interesting.  Of course Cage's philosophy was all inclusive, so that just about anything could be, conceptually, a "musical" composition.  But this quote actually made me think of Edgar Varese more than anyone, as he routinely, and successfully IMO, incorporated all sorts of "noise" into his musical vocabulary. This led to incresing use of all sorts of electronically produced noise by modern composers (synthesizers, etc.)

However, was Cage's pursuit of sound vs music a dead end?  Are composers still incorporating non-musical sound into their vocabulary?  I'm probably just out of touch with the avant-garde, but it seems to me that composers in the past 20 years or so have returned to using musical tones in their compositions.  Or is it just that those who went the Cage route are now producing multimedia "events" and "performance art" that are staged in spaces other than concert halls?

I was just provoked by the Cage quote.  Discuss amongst yourselves, please!