Book I of African Polyphony and Polyrhythm closes with Simha Arom dividing the functions of musical instruments from the Central African Republic into five different categories:
- The most important use is their modal and/or rhythmic support for vocal music.
- Sometimes, such as with the Banda horn ensembles, they are purely instrumental.
- For transmitting messages that would otherwise be spoken, they use wooden slit drums or whistles.
- In order to create a connection with supernatural powers, the community uses certain instruments.
- Some instruments are rarely used because they are symbols of spiritual or tribal authority. For example, drums represent the ancestors of the Nzakara.
There are a number of generic intstruments used by many different tribes such as xylophones, harps, the mvet (harp-zither), the sanza, and many different kinds of drums used for rhythm.
There are also vernacular instruments that are exclusively used by a people. For example the Mbenzele and Aka pygmies are known for the end and side-blown Banda horns. The Ngarka are known for the ngombi, a ten-stringed arched harp.
Music, Polyphony and Polyrhythm 