People were playing Bach on these banjos.

There are some people who doubt the African origin of the banjo. But even a cursory look at these instruments kind of puts to bed any doubt.

It was no longer a social instrument. It was now a performance (instrument) by clowns in blackface performing a very racist stage show to a seated audience.

When it was taken out of the hands of African-Americans and put into the hands of racist white performers, the music and the instrument specifically took on a completely different form and behaved in a completely different function.