Dinosaur Jr.

We all get excited when our favorite old bands reunite, and we tend to overlook the fact that the musicians probably hate each other and are only getting back together because their solo careers have stalled. But few bands have been more public about their mutual dislike than Dinosaur Jr. After singer-guitarist J Mascis kicked out bassist Lou Barlow, Barlow’s other band, Sebadoh, went on to skewer Mascis in interviews and in songs like “The Freed Pig.” That didn’t bother Mascis much: When the Breeders recorded a cover of “The Freed Pig,” Mascis was the producer. Of course, Mascis isn’t what you’d call a sensitive soul. In one of Dinosaur Jr.’s early breakthrough songs, he described his personal philosophy: “Everyone’s idea of fun — repulsion!” Years later, in the band’s post-Barlow alt-rock radio hit he sang, in his customary laconic style, “Feel the pain of everyone/ Then I feel nothing.”

All that antisocial attitude was pretty damn cool in the late ’80s. Without Mascis’s painfully loud guitar ripping through American clubs, the alt-rock explosion of the ’90s probably would not have happened. Let me put it this way: the last time I saw Dinosaur Jr., the opening act was Nirvana.

So, nostalgia explains why Mascis, Barlow, and the band’s original one-named drummer Murph reunited in 2005, but it doesn’t explain why the 2007 album Beyond was so good. And it doesn’t explain why the new album, Farm, sounds so exciting and vital. Maybe Mascis and Barlow and Murph still all hate each other, and maybe they only got together because they want our money. But they sound as if they have rediscovered the fact that they love making music together.

DINOSAUR JR.: The Casbah, Sunday, June 21, 3 p.m. 619-232-4355. Sold out.