I remember back in the mid 60s when we had some gen-you-ine Hootenannies of sorts in Kansas... Once, a fiddler came and played some nice 'old' tunes--then, a few weeks later, I met two brothers who played guitar & banjo and were looking for a fiddle player ...so I kindly offered to get them together. *grin*..It was an educational experience! They talked a bit and compared stories and decided to try some tunes...and the fiddler said "I know a bunch of nice "A" tunes..."...well, you can guess how it went...they didn't all know or agree on WHICH tunes were 'A', etc...they did play a bit and knew enough to share some things, but they all knew early on they were not correctly matched!

I do wonder though at just how hard it is to switch keys for a banjo or fiddle player..being an autoharp player, I have more than once been blindsided by little bands who have decreed that tune "X" gets modulated in the middle.("Silver Bell" comes to mind)

I see banjo player use capos, and I know fiddlers who CAN play more than one key without re-tuning. I guess it is just harder, and they'd rather not. (Like me trying to play various keys on a recorder...the fingerings are jusr easier if I switch instruments)