If cheap can openers could sing, they’d sound like Dinosaur Jr’s J Mascis, who stops and starts in creaky, cranky fits. The job gets done, but it’s rarely pretty. If this Smurf look-alike has become God to a new, grungeful people, it’s thanks to the soaring emotion that flies from his guitar. And a loose, live-in-the-studio vibe allows Mascis, whose unorthodox approach veers between Neil Young’s raucous chording and Jerry Garcia’s filigreed solos, to really rip here. What keeps the enterprise somewhat earthbound are his sidemen’s clay feet.