Dinosaur Jr. set the standard for convulsive indie-rock guitar fireworks in the Eighties. Incredibly, the band’s original lineup — guitarist J Mascis, bassist Lou Barlow and drummer Murph — hasn’t lost a thunderous step. On the second disc since the band reunited four years ago, Mascis moans come-ons like “saaaave me” with the scabrous drawl of a backwoods bridge troll. Avalanching metal riffs and spit-polished solos reach for the sky with a classic-rock charisma the band never went for in its youth. When Mascis wonders, “Should I take it home?” at one point, it’s the first time he’s sounded like the choice was pretty much his. Now, that’s progress.