Interesting post Derek. I've recently picked up the biased opinion that almost everything in the world is objective. Even the definition of subjective is objective.
Everything we can think of is defined entirely by it's relationship with other things. And these other things are defined entirely by their relationship with other things. Eventually, things start to be defined by other things which, ironically, are defined by the things we were originally trying to define. At this point, we realize that nothing is certain and that any subjectivity is founded on bold assumptions.
I think that music is relative. It appears absolute because human beings are wired similar and therefore are affected similarly. I think that an interesting question is: If all humans were wired the same, would music be absolute (all cultural and acquired differences aside)?
The definition of music must be based entirely on how humans perceive it. Why is all music sound, but all sound isn't necessarily music? Each individual human mind makes the distinction between sound and music, and that is why it is relative - because no two people are the same.
Hi Jacob, I meant semi-tonal.
"But who came up with this stuff? Individuals singing their own folk music, sure, you find variation, but who in a culture first decided what was and wasn't allowed? If anyone?"
I think that the consonance, or lack of tension, in octaves and fifths may represent a number of positive things to people, as opposed to the triatone, which was thought to be evil even in the 16th or 17th centuries. If I was a primitive man 5000 years ago, I would choose to endorse the former. This is over simplistic but I have to go now.