tutti flutti

Yes, I know you experienced and confident musicians sometimes can't understand someone being reluctant to jump in but some people are just naturally more timid - it doesn't mean they can't play or that they can't make a valuable contribution!

Round these parts (Lewes, East Sussex, UK and environs) we have a session leader who calls on people in turn to sing, play or say "I don't want to lead but can we play John Innes No 6" and then someone else will lead it. Occasionally someone will leap in but nobody ever gets to dominate.