Cave Singers frontman/guitarist Pete Quirk doesn't need a band, really. He's got a vocal delivery so weathered and lived-in thin as a middle-aged woman's croak, almost, or a limited Perry Farrell that it'd even be a devastating weapon sans instrumental accompaniment. His voice speaks woeful volumes and drips spilt hard liquor even before one realizes that he's lamenting loves lost. With bandmates Derek Fudesco and Marty Lund at his side, however, Quirk is all but unstoppable; this Seattle trio casts a potent, rhythmic spell accented by warbling harmonicas, tambourine slaps, and acoustic guitar slashing away on its intimate, hard-folk new masterpiece, Invitation Songs. Curiously, they're sharing the stage with Black Mountain, a genre-hopping Vancouver-based quintet who spent its self-titled 2005 debut leap-frogging from one '70s radio trend to the next fake disco, fake war-protest rawk, fake Black Sabbath with a disarming nimbleness and ease. The former's authenticity and sincerity would seem to clash with the latter's up-with-irony opportunism, no? This may be less of a problem than it appears. Remember: Variety's the spice of life.