I sang several times at Middle bar, Anchor at Sidmouth this year. My first chorus song was dragged back in the timing - one of the regulars standing near said " you won't win! ". At the 3rd chorus I smiled and announced " in your own time", much laughter, really enjoyed that session. Another time sang with trio, much joining in - got three songs which surprised us.

Many issues raised here are about manners and that's hard to impose.ive never been to a 'jump-in ' singaround, prefer a " you're after them " from an MC. I agree, keep the intro chat brief and be prepared to change song to finish a session on a chorus, not a long ballad, long story or unknown new piece. No 8 applies to booked performers at clubs as well, remember where you came from!
Here's to all the fine well mannered singarounds that work well. Enjoyed the list Acorn4.