I would second what Les From Hull said, heartily! One should be thinking of two or three choices of what you're going to sing or play next as soon as your turn is over. Then, given what the person just before you does, you can offer a change of pace or mood.

Some other comments based on above postings; While too big an audience can be a detriment, I think you need at least one (hopefully the pretty blond !. We all play better when someone is listening - besides other musicians.

On this side of the pond (USA), in the singaround/jams I attend, it's pretty rare to hear unaccompanied singers. Most of the musicians in our circle play an instrument and expect to join in with the singer. Once in a while you get someone who is not very good about backing off when a soft voiced singer is up, but if the singer doesn't give them "the eye," it may be mentioned to them afterwards to be more sensitive about their volume.

Our group is fairly ambivalent about taking individual lead breaks between the verses. Usually banjos, fiddles and mandolins can sketch something out, guitars not always. We generally know who is a "lead" player and who is not. Sometimes we do it unison style. It all depends on good musical manners, and generally, in setting a good example.

We tend to call the more unorganized, jump in when you get a chance, type of jam an "animal jam" - they tend to be full of testosterone & egos, but can be real fun with the right amount of libation.