Here in town we have a Sunday night Blues open mic. It's very popular, and make no mistake, this is a tavern that would be mostly empty on a Sunday night otherwise. I used to joke with my then girlfriend that the bar down the street where we used to hang out (with no live music) was full of people with a neuroses about the looming Monday morning and back to work. After discovering this open mic up the street, I never went anywhere else. If I couldn't make the Sunday might blues session, I stayed home.
My point? Well, the crowd tends to form itself from the music, not the other way around. True, some of these folks are drunk, but I've never seen a lick of trouble in the place. Even the occassional spilled drink is met with a profuse apology, both given and accepted. The reasonable analysis? The folks who regularly attend these things are there because they love the music. I know I do.