There have been a slew of them on the newsgroup

rec.music.makers.acoustic

I only recall a few:

Q: What is the difference between an onion and a banjo?
A: You cry when you cut up an onion.

Q: What would happen if the banjo were left out of a bluegrass band?
A; The pieces would fail to sound the same.

Q: What is perfect banjo pitch?
A: One that doesn't hit the sides of the garbage can.

Disclaimer: The opinions expressed by these jokes do not reflect my own.

Murray