-
It was a long time in man’s history (early medieval timeframe) before mankind figured out a way to write and describe that natural thing known as music. Harmonies were especially difficult (think monastic chants to baroque harmonies). I originally thought that the sounds were the product of how we played them (major or minor or 1, 4, and 5 or 2, 3 or 6 progressions). Then I changed my paradigm. The sounds are as @jumpinjeff says… a result of how our brain interprets those vibrations. Then we just use words or labels to try to describe and communicate to others so we can teach and learn how to replicate music. So they kind of just “are” that way. I am fascinated by the difference in emotion between major and minor. I used to tell my employees or kids having a bad or sad day that they are only one half step away from a good or happy day and demonstrates it with a A and Am chord. Can they make that half step?
Great and fun question.