African xylophones exist in several forms. A broad distinction can, however, be
drawn between those that use a common resonator for all the keys or no resonator
at all other than the space between the keys and the ground itself, and those instruments
that use an individually tuned resonating chamber for each key. These
individual resonating chambers are usually made of calabash. The Mexican and
Central American marimba is of this second type. This type of xylophone with
individual resonating chambers is, once again, found throughout Africa south of
the Sahara, from Senegal to Mozambique.
In addition to the use of these resonating chambers for each key, a small hole cut
in the wall of each calabash and a vibrating membrane stretched over this hole to
produce a desired buzzing or humming sound is a very general characteristic. In
certain African xylophones, the timbila of the Chopi and the Royal Nkoya xylophones
of Zambia, for example, the vibrating membrane is not stretched directly
over a hole in the calabash. It is instead stretched over a small circular plug, which
protects the membrane. The entire plug is inserted into a hole in the calabash
resonator. In Africa, the membrane is most frequently made of the thick part of the
web wall of a ground spider. The web is stretched over the hole made in the resonator
and fixed in place and protected with a small ring. In the Americas this vibrating
membrane is most often made of the intestines of a pig or monkey