Unfortunately I don't remember as much as I should from my music history class (college daze) But there was a group of greek philosophers who studied music, almost to the point of a religious cult. They where way before their time and where responsible for catorgorizing and naming the diatonic system and modes, the harmonic structure, the overtone series, and many tunings still used today. I believe they gained most of there inspiration from birdsongs.
Don't qoute me on any of this, I would strongly suggest researching it if your really interested. I can't remember the name of the philosophical group but believe it had the word phrygian in it. I know they had a book that was translated with all there beliefs and findings in it.