Though Dave Grohl earned immortality as one-third of Nirvana, his current band is also sneaking up on greatness. Employing the same soft-to-loud dynamics as his old grunge outfit, the drummer-turned-front-man now pursues a more flexible, poppier strategy, blending slashing guitars, lush melodies, and soul-on-fire vocals to fashion cathartic mini-epics like “Erase/Replace” and “Cheer Up, Boys (Your Make-Up Is Running).” With their auras of longing and loss, “Let It Die” and “Long Road to Ruin” could be heard as eulogies for his late pal Kurt Cobain—or simply the reflections of someone who’s grown up gracefully without dousing rock and roll’s adolescent fire.