....well, more accurately, Botswana rather than South Africa.

There are quite a few YouTube vids of local guitarists, playing and singing.

Here are a couple of examples:
Mosanki Mokete
Kagiso
There are lots of others to hopscotch through. They're all fabulous performers!

I'm intrigued by the fact that many of the guitarists are playing with only one bass string - the A and D tend to be missing.

The stringing seems to be similar to the lap dulcimer - a bass drone, three higher melody strings. Other African acoustic guitar styles (say from Mali or Senegal) use a thumb and index finger picking, and often a capo. I guess this is to emulate (or has grown up in the shadow of) multi-stringed instruments like the kora. I can't think of a Southern African equivalent instrument that might have given a similar influence.

I'm sure the four-string guitar is through choice rather than necessity.

Any thoughts, please?