Overtone music of the Wagogo
The Wagogo are known for their music with the harmonic series. They use the 4th to 9th harmonic from the natural overtone series for their melodies. Apart from the Xhosa, the Wagogo are the only African people to use vocal harmonics. The singing technique is similar to the Kargyraa of the Tuvinians, i.e. an undertone singing combined with overtones.
Many thanks to Palmer Keen for bringing me to this clip.