greenword, I think in most sessions (and presumably sing arounds etc) even if there is nobody in charge, an understanding develops between the regulars and most people are respectful of their fellow players and singers and follow whatever "rules" exist quite naturally. Occasionaly you will get somebody that genuinely does not know that what they are doing is upsetting others but most reasonable people will take a gentle hint if they are doing something like that.

Some things like talking over a singer are plain rude in everybodys book (at least I hope so) and unfortunately, there is a small minority of very rude people who have no conideration for others around. Unfortunately the 1 or 2 that do behave badly can and do ruin things for everyboy else.

Jon