"The drums were made from hollowed-out tree trunks with leather skins.
Lumps of beeswax, on the drum skins, were used in tuning the drums, and can be seen on the middle drum.
The tallest drum is called kurugoma(kuru meaning large), the smallest mundindi (meaning small), and the middle drum nkinzo.
When more drums were brought to a workshop, only three were normally used at a time.
However, at the party, with its atmosphere of informal celebration, extra drums were used. .....
The drumming in both the neo-Kavango and traditional songs used cross rhythms and additive rhythms in patterns in which the set of (usually three) drums acted individually while producing combined patterns."
excerpt from: Kavango Music by Dave Dargie
Dargie Dave - Kavango Music
Dargie Dave (1988) Xhosa Music. Cape Town: David Philip
Ankermann, B. - Die afrikanischen Musikinstrumente
Bebey, Francis. African Music: A People's Art. New York: Lawrence Hill, 1975
Dagan , Esther A. - Drums : The Heartbeat of Africa edited by Galerie Amrad 1993
Wieschhoff, Heinz : Die afrikanischen Trommeln und ihre außerafrikanischen Beziehungen. Stuttgart 1933