This is a tradition in the Mongol area. It was exercised by monks. First time I've learned about this was sometime in the eighties through German tv. You get a lot of hits when you search for Mongolian Throat singing. For instance:
https://www.youtube.com/results?search_query=mongolian+throat+singing
https://www.youtube.com/results?search_query=polyphonic+overtone+singing+mongolian

I was really impressed with this one here:
https://www.youtube.com/watch?v=nPu9XMMY1Y8


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