Yes, I would agree with Howard, though I don't know much about singing or Sidmouth.
When I go to dances without a partner I need to make it clear that I want to dance,ask people or stand on the edge of the dance floor and look hopeful rather than sit in a back row.
I guess that if you go into a singaround it might be a good idea to ask who is in charge and make yourself known.
A festival is so short - the programme is not always very informative about exactly what kind of event each is - most people have been coming for years and 'just know'.
I go to Whitby and there is always a prefestival discussion on Mudcat of someone asking 'where is the best place for .... (whatever that person wants).
Whitby, Chippenham and Chester (maybe others) have Youth sessions where some of the younger booked guests lead and us oldies are excluded so I'm not sure if they sing, play or both.