Gordon Kennedy has a gift for crafting poignant roots tunes. For Eric Clapton, he helped pen the Grammy-winning “Change the World,” blending a gently epic declaration of love with smooth blues and touches of R&B. He’s been one of Bonnie Raitt’s favorite songwriters, too, working behind the scenes on the sly kiss-off “I Can’t Help You Now.” And he got heavy with Southern rockers Blackberry Smoke on “Bottom of This,” railing against the crush of 21st-century life.