Agreed with most of that Julian, but there are people who enjoy being in a group of others singing and playing music, while not taking part themselves. Maybe they have no musical ability (or think they don't - I believe many people have more ability than they themselves realise); or maybe they just don't feel the urge to sing in front of others, perhaps through shyness or lack of confidence; or maybe there are other valid reasons to do with health or disability which would prevent them being able to take part.

Nevertheless these people (and we have a few regular attendees at our club singarounds, who never ever sing themselves) enjoy being part of a social gathering and are happy to be there. So I don't think it is always a loss to such people if they don't sing.