I'd no doubt that the format went back deep into history, but applying the sort of rigour the BBC TV word origins programme might - the first valid evidence (ie. written/printed and applied to the correct subject in question) to feature in this thread at least must be the 1976 - South Yorkshire example

I first encountered the word when a friend who had just moved to Brighton wrote to me about the folk gathering he had discovered in nearby Lewes which was called a singaround. That was 1978. What I can't establish so far is whether the organiser, Fred Baxter had put it in print ie. in some advertising. Fred did however think he had invented the word in relation to the classic format we now know as a singaround - by 1975. Does anyone have anything from the Lewes area 1975-1978?

Look forward to further developments...

Ian Fyvie