Formed in Dayton, Ohio, six years ago and signed to Fat Possum Records soon after on the recommendation of Patrick Carney of the Black Keys, the Heartless Bastards may be the meanest-sounding, female-fronted dirty blues band in America. Erika Wennerstrom’s voice is an instrument every bit as snarling and jagged as her guitar, and her songs — hammered home by the rhythm section of drummer Dave Colvin and bassist Jesse Ebaugh — pack a vicious punch, too. The Heartless Bastards scored heady critical acclaim with their first two albums of emotionally volatile garage rock, 2005’s Stairs and Elevators and the following year’s All This Time, but this year’s The Mountain — recorded in Wennerstrom’s new hometown of Austin with Spoon/Patty Griffin producer Mike McCarthy — is the band’s most compelling release to date. Prepare to be awed — and pummeled without mercy.