I really think that all sessions need to be led. If there is no clear leader then usually the session will deteriorate to the stage where the only few singing are those who are ill mannered enough to take someone else's turn.

I was at a session last Saturday and someone said to me "Why aren't you singing? You have some interesting songs. Don't be shy. Just barge in"

Well, I had gone to the session because I thought it was a social occasion. If I had wanted to 'barge in' I would have gone and played rugby instead.

So, if you want to run a session, make sure that you have a leader, otherwise the majority of your members (those who are polite enough to have normal social behavior) will not get to sing.

Bert.