"*But* there is no doubt in my mind that the natural tendancy is to prefer just thirds for excellent physiological reasons."

Dustin, in the early forms of Medieval European church music, the fourths and fifths were preferable to the thirds. Organum and Gymel. Thirds and sixths came later in the Faux Bourdon era.

"Dissonance and Consonance I think are fairly well based in physiology, and one measure of this is that the most consonant intervals are the most universal"

We've got a cultural semantic problem here. Dissonance and Assonance or Consonance are interpretations. One person's dissonance may not be another's. I don't agree that you can reduce music to physics or physical interpretations of audio responses. We're talking about two different worlds. Not enough studies have been done in the world's music to indicate that there is a universal response to dissonance and assonance/consonance. The music of Bulgaria is pleasing to it's singers and the use of the minor second intervals or major sevenths is part of the singing. It's not dissonant to the singers.

Frank Hamilton