And sessions is sessions and singarounds are singarounds.

The OP went to a folk club to see a band and paid good money. She got as she described it:

First a selection of floor singers ambled on and after the usual false starts ("oops- a bit high; I'll try that again", etc.- haven't these people ever heard of pitch pipes?) a singer came on who stumbled to the end of the first verse of her chosen song, then forgot the rest and had to be helped through it by members of the audience. As she sat down, to cries of "Well done" and "We got there in the end", one of my friends whispered to me "People actually PAY to listen to this???" in astonishment

If that did not reperesent folk clubs I have been to then I would have contradicted her as Dick Miles has done and said generalising from the particular. I disagree with Dick, that descrition is far too common.

I am happy to give people chances; but I would prefer them to sing in tune and know the words to the songs they are singing. Especially when they have written them themselves.

Is that really too much to ask?