Nashville - best spots for open jam sessions, what music to prepare?

I haven't been there in many years, but it used to be all the clubs on "lower broad". That is Broadway St. near Ryman Auditorium, between about 2nd and 5th Ave.
You may get some stink-eye if you don't have your own bass.
 
i was up there last November and Broadway was a veritable zoo, but Taylor Swift was in town that night so what more would you expect.