It has structure
It has form
It has sonic content
It has a performance context
The original score had a time signature and was written on manuscript paper
and you miss the point entirely if you think that it's "about" nonmusic
but nice to see that the hissy fit is over
"A great list up to the Riley which I'm afraid I don't know. I would tentatively add Sergeant Pepper in its place."
I find that extraordinary that you have never encountered InC
but Sergeant Pepper is most over rated IMV
Regardless of whether 4'33" is or is not music, I would want a lot of convincing that any music has been written, or written differently, because of Cage's piece. What that has done is to generate a great deal of writing. Music makes music history: critiques don't.
Perotin Viderunt Omnes
Palestrina Missa Papae Marcelli
Petrucci Odhecaton A
Peri Dafne is lost - so Monteverdi Orfeo
Bach das Wohltemperierte Clavier