I was inspired to write Ubangi upon hearing the complex polyphonic vocal music of the Aka people. The Aka live around the Ubangi river in central Africa (hence the title of the piece). The dense contrapuntal textures of their music are created by layering of repeating melodic cells of irregular length.
This irregularity causes a constant shift in the relationship of the voices and in the resulting texture. Their music -- and the current piece -- doesn't really have downbeats; instead, they have a fast microbeat which is common to all voices. Aside from that commonality, the voices move in almost complete rhythmic freedom from each other.
In Ubangi, I didn't attempt to imitate Aka music; rather, I employed the structural and rhythmic concepts of their music to create a piece I can call my own. The tonal/harmonic and the large scale form of the piece, have no connection to Aka music. The thematic material of the piece is presented in two thematic groups, each of which grows from one solo line by adding new layers in the Aka manner.
Each group of themes is in a different tonal area. This presentation is followed by a development in which the themes from the two groups intermingle and mutate. A central episode in this development is reached at the point of furthest tonal remove from the original tonal areas (in technical terms, the tonal area includes the complement of the set on which the second group is based, and is at a tritone relationship to it).
The music builds to a climax which coincides with the reappearance of the original thematic material in reverse order. The various layers also appear in a different order, creating a different perspective. The first thematic group (which now appears last) is modified to fit the tonal area of the second group (now appearing first).
The various layers peel away leading to a short coda. Mention should be made of two other, non-Aka, African elements in this piece. One is the piano ostinato throughout the piece, which is an actual bell pattern from West African (Ewe) music. This ostinato provides a timeline against which the other irregular elements appear in context. The other is the hocketing of the opening theme at the coda, this is characteristic of the Ba'aka pygmies (neighbors of the Aka).