I feel for you Marion. It is an interesting feature indeed, to have unsolicited accompaniment...

Though the majority of musicians probably could not be versatile enough, the players that can pull it off are great, and it can make the evening go smoother, but the eclectic nature of the performances can still get lost in the translation. I would call it a melting pot effect.

But between you and me, unaccompanied singing is a fantastic art, and the people who do it should NOT have to go against the grain of the evening... Please keep doing it, Marion, you have already broken the ice at that venue, and they will (ought to be) more cordial next time...:o)