Thanks for this very interesting and informative post. I have not yet had a chance to read everything in full, but I will.
In the meantime I came across this item from Theodore Finney's "History of Music" wherein he says: "That tenative perception of the naturalness of the diatonic genus was the first great step in the direction of modern tonality. Had the Greeks settled on the enharmonic genus (there were three types of tetrachords: diatonic, chromatic, and enharmonic) for instance, the whole course of Western musical development would have been much different. We might have inherited a music similar to that of India."
I don't quite understand what Finney means by this, but I would be interested to know how it was that India's music remained where it was and Europe went on to develop Brahms, Beethoven, Schubert etc.. Great post, btw.