One of his composition teachers, Arnold Schoenberg, thought so.

What about ritualistic music?

How about composition of sound with a purpose. Like you noted, music isn't always merely entertainment but can serve other uses.

Prayer.

How can you find an absolute definition for such an etymologically strange word? Once you try and put a boundary on it, someone's going to move it.

Why is John Cage seen as such a revolutionary? How much more abstract can you get than with the ancient Greek's humanly inaudible "Music of the Spheres"?

It was stated earlier that a baby crying isn't music.

Well, how many times has such a sound been recorded and used in commercial rock recordings? Second track on The Wall is probably the most obvious.

If some concept artist/composer put a bunch of neglected babies on a concert hall stage for twenty minutes, I'm sure pretty much all of them would start crying.

You would then hear recognizable intervals, beats, rhythms occurring between the crossings and interruptions of their voices. At that point, you'd have to admit it's fairly musical.

I hope I didn't give anyone any ideas.

Interesting points you have there.

Well, I really don't think there is out there an absolute definition for this word, but maybe at least it makes you think a little.

I never said John Cage was that revolutionary, in fact I don't think of anybody who is that revolutionary, there are only small steps in music, and sometimes the steps even go backwards.

Crying isn't music. You can use a baby's crying to make music, which is different.

Crying has pitch, duration, timbre, rhythm, volume...etc

Yes, and that's exactly why you can use a baby's crying to make music, but you can't tell me that every time you hear a baby cry, you call it music, or do you?

I don't rack my brains over it.

Can you explain why it's not music?

Haven't we had this discussion a million times already? It's like asking some philosophical question, like, "how do we really know we exist" or "what is ethics?". There's never a definition everyone can agree on.

Thankfully noones enjoyment of music has ever depended on their ability to define it.