Boston's Pile is a zero-compromise band, which helps to explain why it has such a rabid core following and why it hasn't attracted a larger audience. One suspects this is exactly how frontman Rick Maguire wants it. Taken alone, his voice has all the chesty resonance of Eddie Vedder's, and the individual guitar melodies sketch out a spiky but not unnavigable terrain. It's the big picture that proves most treacherous for casual listeners, who may find they've been led off the expected rock path into a mutated thicket of malnourished Venus flytraps. While new release A Hairshirt of Purpose (Exploding in Sound) doesn't sound like the ideal point of entry for someone unaccustomed to aural punishment, it's actually the most inviting album Pile's ever produced. The angry-polygraph ups and downs rarely leave the graph paper, and Maguire's arrangements require no protractor to solve, even ascribing to a kind of centerpiece-and-interlude order (though centerludes and interpieces seem more appropriate). If you've tamed the flytraps and beaten the polygraph, there's "Hissing For Peace," which resembles a redlining centrifuge missing a few screws. That's just Pile, a frayed stretch of elastic that lives for the snap. Gnarwhal, Pope and Treadles open. Tickets $10.