Meself says it well (although I also wonder if it was Celtic Colours the poster meant). If a Cape Bretoner pays good money to listen to a performance, then they darn well listen. I'd guess most of us would think it highly rude to sing along unless invited.

I do remember some messy weekends at the long defunct Atlantic Folk Festivals in Nova Scotia. Lots of drunks, a few fights, a bit of mud-blood-and-beer, and no doubt a fair amount of random copulation, although not in the public eye.

Other music festivals, like the Bluegrass I'm more recently familiar with, consist of people listening to stage performances, and participating enthusiastically in 'field pickin'' when the stage has no performers. It's my favourite part of the festival, going around from campsite to campsite enjoying the random assemblies of musicians. Often many of the stage performers are also jamming with any musician who shows up at their campsite.