I took a music course back in college in the Dark Ages in which one of our early assignments was to come up with a definition of music. I'm not sure I quite remember what it was and what else besides music would have fit in it, but I do remember that it would have excluded John Cage's compositions (well, except for maybe 4" 33'). The relevant part of the definition was that the composer pretty much knew what it was going to sound like when it was done.