Ah, but Martin, even in the exalted circles in which you operate, aren't there some players less experienced than others? Aren't there some tips you could pass along to players who are basically musically literate but who could contribute more to a group session if they just got a bit of advice from an insider?

For example, what if a folk/country-blues picker with forty years of playing experience wanted to sit in with you and your bluegrass buddies? Someone perfectly capable of simple full-chord strumming on G, C and D7 who would be glad to do more, but who might not be sure just what kind of embellishment/variation, and how much, to inject? Any advice?