What singer Anne-Maria Hefele is performing is a style of overtone singing, and it's one of the most otherworldly sounding things I've ever heard. The whole thing is worth a watch, but the part at 3:25, where she moves the fundamental and overtone in opposite directions, had me shaking my head in disbelief.
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That is damn cool.
For anyone interested, I ran across a little about the science behind this overtone technique.