Hope no one minds if I add to this thread. It's been a long, long time since I tuned in here. Of all the things that most grate (to me) in jam sessions, singarounds, etc. are those who cannot keep simple time or tempo. It's an absolute killer when someone is a beat behind or either speeds up or drags everyone down. Of course, these two things are also a pretty good way of uninviting unwelcome crashers, too :o).