This is one of the many reasons Pentatonix is just an amazing group. I saw him do this in person. 
Avi Kaplan Overtone Singing Lion Sleeps Tonight - Pe...
Avi Kaplan Overtone Singing Lion Sleeps Tonight - Pe...
I have a video of him doing this on my phone from the concert I took my son too.
that's just insane.
It really is.
gotta love Tuvalan throat singing
thats frigging awesome
that was amazing!
he is much better at it than Sheldon Cooper is. 
Sheldon Cooper Throat Singing
Sheldon Cooper Throat Singing 