There is an old LP from Folkways, with a fair range of genres, both vocal and instrumental, but nothing quite like what John was describing. The most extraordinary was the sound of aeolian flutes - these were bamboo poles with a slot cut in each segment at a random angle, set up on a beach to be sounded by random gusts of wind, and intended to guide the souls of the dead on their journey out to sea. Unearthly microtonal dissonances.

I have a book on Kanak music, from Bougainville island off New Caledonia. Again, not much like what John was describing. A lot of the vocal music has extremely narrow range, and some of it uses microtones you probably can't easily represent in MIDI. There are a few choral pieces that use yodelling/hocketing techniques like those you find in Georgian music.

There are also ethical issues. Some of this music belongs to specific peoples, families and lineages - "belonging" in a very strong sense, that it's unthinkable that anyone else would play it. You need to know which pieces are fair game for the sort of dissemination John had in mind.