Usually, when we turn up for a show at the Black Cat’s backstage, we expect a relatively subdued affair. The smaller of the club’s two stages, the backstage usually hosts smaller, lesser known acts–bands who haven’t yet built a large or fervent enough fan base to fuel a raucous mainstage set. Thursday night, however, proved to be an exception to this rule. While both of the night’s performers are relative unknowns in these parts, that…