Songs in parallel fourths are the most common throughout the many tribes that Simha Arom has studied. Most of the time there is a fluctuation between 4ths and 5ths and an occasional 3rd in order to preserve the pentatonic sound and not veer off into polytonality.
The most widespread musical scale is the anhemitonic-pentatonic scale. It can be organized in five different ways: (Arom, 24) It is the same pitch set with just a different starting note.
Perhaps, singing this scale with an overlapping and staggered form (as André Gide mentions in his description of the ‘Tam-tam’) results in what he describes as “harmonic richness”.
Also, note that if a D# is added to inversion no. 5 above, you have the traditional blues scale A-C-D-D#-E-G-A. One can imagine how African-American blues evolved from this anhemitonic-pentatonic scale when sung with certain vocal inflections.
Here is a hypothetical arrangement I created of four voices each singing the same melody but not in unison. Notice that the 1st time I evenly stagger the entrances of the scale. The 2nd time, the scale has a “jagged” layering. Both ways create an “harmonic richness”.
Voice 1 D-E-G-E-G D-E-G-A-G
Voice 2 D-E-G-E-G D-E-G-A-G
Voice 3 D-E-G-E-G D-E-G-A-G
Voice 4 D-E-G-E-G D-E-G-A-G
Furthermore, by moving two lines in parallel motion but with different starting notes you can arrive at a succession of 5ths. Below is a hypothetical melody I created of a pentatonic scale demonstrating what some ethnomusicologists describe as a hybrid of medieval organum:
Movement only in parallel 5ths using the pentatonic scale
Upper voice: G-A-G-E-D-E-G-A-G
Lower voice: C-D-C-A-G-A-C-D-C
Arom states that tribes in the Central African Republic speak in a tonal language. If one sings a particular word, it must use the same intervallic motion or else the word will cease to have meaning. I understand this to mean then intervals heard in spoken language are similar to what Arom has heard and recorded in their sung form. That is, the pitches heard in song must follow the language’s tonal scheme. Does this mean that the tonal languages of some tribes of the Central African Republic use pentatonic intervals?