The Gyuto Monks
Artist Bio:

The Monks of Gyuto developed and perfected a distinctive multiphonic chant, in which each monk sings not a single note but what sounds like an entire chord. “This remarkable, transcendentally beautiful sound,” notes Robert Thurman, religious scholar at Columbia University, “is thought to arise only from the throat of a person who has realized selfless wisdom.”
The monks have toured periodically throughout the world and have released several recordings, the most recent of which is Tibetan Chants for World Peace