The Jayhawks’ best ?moments depend on their two songwriters’ bipolarity — when Gary Louris’ sunny, ’70s-pop sheen gets scuffed up by Mark Olson’s disheveled folk rock. That tension made them critical darlings until the partnership dissolved after 1995’s near-breakthroughTomorrow the Green Grass. Louris and Olson reunited as a duo in 2008, but here they rekindle the band’s singular dynamic: a sugared pop strut (“She Walks in So Many Ways”), tempered by the heart-wrenching harmonies and sinister vibe of “Tiny Arrows.” Ignore the mouth-breathing rock bangers, andMockingbird is as comfortable as well-worn denim.