An overtone is a frequency greater than the fundamental frequency of a sound. A harmonic series (overtone series) is a sequence in which each frequency is an integer multiple of the fundamental tone. Overtone singing is a traditional form of singing in many parts of the world.
Audio:
OVERTONE SINGING UMNGQOKOLO by Xhosa women from SOUTH AFRICA
Visual:
Prewar AFRICAN Rice culture mask dance
audiovisual:
polyphonic overtone singing - explained visually by
Anna-Maria Hefele