Not an obvious question with an even less obvious answer. Another reasonable question would be “Does music exist?”. If some thing A doesn’t exist then asking “What is A?” should have no answer. Here, I propose an answer for when A=music, therefore music must exist (at least for the next few paragraphs).
I had a debate with some friends about this question and I think we all agreed in the end (maybe because it was getting late) that music is what you say it is. That’s a bit of a copout answer, I know, but it’s the only way to get everyone to agree. Let me try and elaborate.
We concluded that if you perceive something as music, then it is music, to you. Interesting little side note: this is how my second theorem came about. We were talking about how anything has the potential to be music, it must only be said to be so. The famously comical example used was our friend’s fart, who from now on shall be referred to as Kris to protect his identity. So the question was brought up a number of times: Can Kris’ fart be considered music? Well if you were passing by and had just joined our conversation you’d immediately make a weird face, similar to the one you’d make if you actually smelled the fart, and laugh at the question saying “of course not, that’s silly”. You might however decide to sit down and join us and after a while we would probably convince you that Kris’ fart can be music if someone says it is.
Can we really say that something exists objectively if it is only defined to exist subjectively and no human on the planet ever perceives it as such. Another important question is: If person A perceives something as music, does it mean it’s music to A only or to everyone else as well?
To put this in context, if nobody ever perceives Kris’ fart as music, then we can say that it objectively is not music and that its being music does not exist. Right about now a light bulb should have gone off in your head. In a sense, if you think about it, music doesn’t exist unless humans exist. This is true of a lot of things I suppose. The difference with music is that the same physical thing which can exist independent of humans yields a nonphysical thing which may or may not exist. This is why this question is so fascinating to me. The self, freedom, and all that good stuff is only relevant if humans exist and no form (not the platonic kind) of physical evidence can be shown for their existence without humans, or with humans for that matter. The existence of music on the other hand is very interesting. Physical existence can be there and there need not be any physical change (apart from the neural connections in the brain) from its existing and not.
The same pressure change in the air can suddenly exist as music where it hasn’t before. A new spontaneous birth has been given. This holds true for other things like beauty. All this to say, the answer to the title question is that music is everything and anything you want it to be.
In some ways, music can be said to not exist at all in the case where no human ever perceived anything as music.