Margarita, that's also the way we normally handle things at our song circles in Toronto. We have the advantage over some of the other sessions described in this thread of having our weekly song circles in people's homes rather than in pubs, and over the years a set of 'unwritten rules' has developed, including one in which the person leading the song is in charge and can ask for accompanyment or not,and can request that others not sing in certain spots. This is generally respected. Newcomers to the song circle are given the 'basic' guidelines, and if they don't pick up the subtler courtesies after a couple of weeks, someone is likely to mention it to them. It works well and we have few problems.