The Spinners came to Barnsley many years ago and I unwittingly upset an elderly lady by joining in on choruses ~ I was much younger then of course
I have similarly come in for criticism at local festivals for joining in
Folk clubs are smaller and I find on occasion those joining in sing and sometimes it's OK sometimes er NOT harmony wise
Folk generally should be participatory ~ lots go just for that, and as said above nothing better for an artist to hear audience singing back even better with singer songwriters ~ "Band played Walzing Matilda", "Caledonia", etc
The whole concept of "Why" guest artists learn songs and arrange them is quite fundamental here too ~ I am pretty sure that there is little demand for people to make CDs to sell as a financial incentive
Folk concerts are a communal activity for the audience or should be ~ I am damned if I am going to sit quietly in a concert where the material is familiar ~ what am I there for in the first place? Not to listen to the expertise of the musical arrangement, necessarily?
Or maybe I have missed the point ~ many attendees are new and my joining is a distraction and I am out of order in that respect ~ a bit like Health and Safety rules
the late Roy Bailey on the final night at Towersey ff and everyone joining in with John Tams "Rolling Home":