In European music, there seems to be an ideal of “clear” and “clean” timbres in music. In many African music cultures, in marked contrast to this, there seems to be a fondness for somehow rough and smoky timbres. After listening to a lot of African music from different parts of Africa for more than 30 years, I have come to like such “noisy” sounds.
These rough and noisy acoustic colors are by no means the result of imperfect or badly build instruments. Instead, many instruments have special devices that are deliberately built to create a buzzing or otherwise “noisy” sound. One of my kalimbas has a little chain on top of the keys that makes a rattling noise. Another one has a crown cap fixed to it that produces a buzzing sound, and I have seem similar constructions with clam shells instead of crown caps (probably the older design, although crown caps are obviously very common now). I have seen other similar devices, like pearls on a piece of wire, little metal rings around the keys (see picture), vibrating needles attached to the keys of an instrument with wax, and other constructions. A lot of creativity has obviously gone into the invention of such devices. Some African xylophones have gourds hanging underneath with holes covered with a membrane made from spider silk that give a special noisy quality to the tone. Some harps have devices made from lizard scales fixed next to the string so the vibrating string will touch them, producing some kind of buzz or rattle. And there are probably some other constructions as well.
Once you are used to these noisy timbres, they are quite beautiful. Another effect is that they make the sound louder. But I think there is more to it. Let me go into some more detail.
Most languages of West Africa, Central Africa, Southern Africa and parts of East Africa belong to the Niger-Congo language family. Most languages of this language family are tonal. This means that there are words or grammatical forms (or both) distinguished only by intonation. Maybe you speak such a language, maybe you don’t. Consider you did. If you hear a conversation dampened through a wall or disrupted by some noise, you might only be able to distinguish the changes of the tone pitch. There might be hundreds or thousands of words with a given intonation pattern, so if you just hear one word, you would not understand anything. But if you hear a longer utterance, this ambiguity will go away. Our brains have a remarkable ability to reconstruct language in a noisy environment or when some part of the speech is damped away. As a result, you might be able to understand the utterance from the pitch pattern alone.
Africans have used this effect for a long time in long distance communication in drumming signals. The drummer, normally using something like a two-tone slit gong, will drum the intonation pattern of a message. The hearer, with some training, can learn to understand it even if the information conveyed by consonants and vowels is lost. This type of communication was used, for example, in the ancient Congo Empire to transmit messages to and from the capital, enabling its rulers to receive and send information with an unprecedented speed. Yoruba drummers use a similar effect with their talking drums to recite praise poems or other texts.
Generally, in a tonal language, a piece of music played on an instrument might evoke language associations in the listener by imitating tonal patterns of language. I don’t know if or to what extent such effects play a role in Shona music, but a lot of examples are known from many African music cultures.
And this is where, I suppose, the buzzing sounds come in. If the sounds are noisy, containing a broader range of frequencies and sound components, the listener’s perceptive system can more easily, I suppose, perceive them as language: such instruments will “talk”, or rather “whisper”, better, providing more acoustic material from which the listener’s brain may form the impression of consonants or other language sounds. This is, at this time, just a hypothesis, but it could be tested in the lab by playing more or less “noisy” melodies to speakers of such languages and ask them to try to associate language with it.
I don’t speak or understand any tonal language myself so I only have theoretical access to such effects and the aesthetic possibilities they might open up in music and the associated poetry. But nevertheless, I have developed a liking for the noisy sounds of African music, to a point where I perceive the “clean” sounds of some European instruments as bland and boring. So I hope to continue to see and hear the crown caps on the Mbiras. Let them buzz!