In Afro-American Folksongs, published in 1913, ,Henry E. Krehbiel describes an African instrument called a zanze as follows:
"The zanze is a small sound-box...hollowed out in the form of a round gourd to the upper side of which, over a bridge, are tightly affixed a series of wooden or metal tongues of different lengths. The tongues are snapped with the thumbs...and give out a most agreeable sound. I find out no records in the accounts of travellers as to any systematic tuning of the instrument, but a specimen from Zululand in my possession is accurately tuned to the notes of the pentatonic scale.with the addition of two erratic tones side-by-side in the middle of the instrument..." [Afro-American Folksongs, p. 68]
Krehbiel continues at another opening:
"I have mentioned a Zulu zanze which is in my possession--. It has pentatonic tuning down to two middle tongues, which emit strangely aberrant tones. The key is D-flat. The tongues on one side emit the descending order, D-flat, E-flat and B-flat; on the other B-flat, F, D-flat and A-flat....Between the right and left rows of tongues lie the two which give out the strange, wild notes A and B." [Afro-American Folksongs, p. 74]
The instrument Krehbiel describes sounds like a thumb piano in today's terms. Other than saying the instrument came from Zululand, he provides no other idea of its origin. Assuming the instrument is authentic, the question came to me as to whether the tuning he describes, especially the aberrant notes, belong to a natural scale. Krehbiel assumes that the tuning is diatonic. I'm not sure that is a good assumption for a genuine folk instrument. For one thing, the pentatonic tuning could as well result from the gaps in a natural scale.
Assuming Krehbiel's description of the pitches is accurate, I transposed them down a half step to C and fitted them to what appears to be an approximation of a natural scale. Does anyone in OMN have a take on this?