Once a month, crowds gather at Northside Tavern for a hot session of trio sonatas and brass quintets. Or wind ensembles and string quartets. Or operatic arias. On a recent Sunday evening, an audience decked out in jeans, multiple tattoos and piercings ambled past the Cincinnati Wind Quintet warming up to perform a Viktor Ewald piece. It's another evening of Classical Revolution, Cincinnati's branch of a growing national network that bypasses the concert hall for bars and nightclubs.