There are so many subcultures going on that it is nonsense to believe that someone is being rude if they join in or don't join in. In the old Seattle Song Circle it was understood (by me anyway) that you would join in with the singing if you knew it..but you were not to overpower the leader, unless he or she was so floundering it had to be done...instruments were more of a problem and we finally just said only guitars. Now, if a person wants no instruments, or all instrumnets, or only flutes, she can say so up front or have a discreet hand signal if they start to confuse her. Some places consider it rude to join in; some expect it. I personally prefer it..singing..but I hate guitars playing the wrong chord..I don't want to hear myself singing a solo and I don't want to hear too many others singing a solo either..one after another after another..what I want to hear is a group singing...I have been confused for a while because people listen adoringly (or seem like it) instead of singing along..I would look around and think..half of them have to know this song...I finally figured out they were trying to be polite. So state your preference upfront, don't act morally superior because it is a preference and not a virtue. mg