At these sort of performances, session members tend to be 'on their best behaviour' so as not to jepordise another performers song/tune. This in turn tends to improve the standard of general performance and therefor the general 'feel good factor' of the performers.
There's nothing an audience likes better than to hear good music played and sung by people who are really enjoying what they do.

I like the idea of 'sining in unison', does this go on a lot at Juneau? Please forward instructions how to get there. :}