Big Jim, in my neck of the woods that is referred to as a Jam. There are some bands around here who do the same thing, rotate players in and out. Mostly blues players,some jazz. The open mics that I go to are "plug and play," you just bring your instrument and plug into their equipment. You can travel light, and if you time it right you can hit a few in one evening.

Its just lke anything else, its what you make of it. I have several friends who run them so I always feel comfortable when I go to one. Then there is the adventure of going to a new one where you don't know anybody. You would be suprised how quickly you can make new friends.

If you are ever on this side of the pond, especially near Buffalo NY, you'll have to check out a pretty vibrant O.M. scene almost any night of the week.

https://www.facebook.com/TheHeenanBrothers

http://youtube.com/watch?v=HEfkNmTToPA