Coincidentally, I just picked up a copy of the Nonesuch Explorer album "In The Shadow of The Mountain" at a used vinyl store the other day not knowing much about it and I can certainly vouch for its awesome-ness. It has several selections which seem to fit the description of the singing style you mention.

Also, another great album from the Explorer series that I can recommend, collected and produced by the same man, Martin Koenig, is "Village Music of Yugoslavia." They're both great albums with some wonderful music on them and have got me very interested in music from that region of the world.