Maybe J Mascis was just not cut out for rock star excess. Modern folklore says he lived in his parents’ basement, even at the height of Dinosaur Jr.’s notoriety in the ’80s and ’90s. But then as now, when he steps onstage, Mascis’ quiet, eccentric demeanor becomes lost in a whirling sea of metal grimaces, violently twirling hair, and relentless shredding. That transformation is analogous to the reason it doesn’t feel right to refer to Dinosaur Jr.’s reconstitution—Lou Barlow and drummer Murph rejoined Mascis in 2005—as a reunion, since its latest offering, Beyond, picks up right where the band left off 10 years ago. At this stage, Beyond won’t re-create the magic of Bug or Green Mind—but, at the very least, it’s an effort any seminal band should strive for when they inevitably reform a decade or two later. Dinosaur Jr. performs with Awesome Color and Dead Confederate at 8 p.m. at the Black Cat, 1811 14th St. NW. $20. (202) 667-7960. —-Maggie Serota