VIDEO: Dinosaur Jr, "Been There All the Time"

J Mascis hates Lou Barlow. And the feeling is mutual. Well, maybe “hate” is too strong. Let’s just say they’ve learned to tolerate each other. And there was more than a decade of bad blood between the two members of Dinosaur Jr. before they got to that point. The drama began in 1989, when Mascis, Dinosaur Jr.’s guitarist/frontman, booted Barlow from the band. (Drummer Murph stayed on until 1993.) Barlow responded by making Sebadoh his full-time gig, writing the acerbic tune “The Freed Pig,” and referring to his old bandmate as a “pedal-hopping . . . dinosaur” in “Gimme Indie Rock.” Yet Dinosaur Jr. are back, and poised to have their biggest year yet, with a new album on Fat Possum/Epitaph (Beyond) and a new DVD (Live in the Middle East). They even signed on to perform at Urban Outfitters as part of a multi-city “FreeYrRadio” promotion sponsored by Toyota and designed to boost interest in college radio. Dino Jr. played the Boston gig a week ago Monday, and they didn’t look like a band in turmoil.

“I wouldn’t say we’re friends, exactly,” says Mascis of Barlow. “Not that we ever were friends. We were just the only people [in mid-’80s Amherst] into the kind of music that came out back then — first hardcore, then the stuff that came after.”

Barlow, who had success with the Folk Implosion as well as Sebadoh, has a slightly different take on the situation. “Apparently, I was annoying.”

But two years ago, Mascis reacquired the master rights to the first three Dino albums and reissued them on Merge. When Barlow and Mascis ended up on a bill with Sonic Youth in Northampton around the same time, they agreed to bury the hatchet and put the original line-up back together.

The old Dino roar was back at Urban Outfitters, just as it is on Beyond. It was like 1988 all over again — angst and ennui delivered at maximum volume. Barlow tossed earplugs out to the grateful few up front. The long-and-gray-haired Mascis didn’t quite smile or emote, but he seemed in the zone with his guitar swaying gently side-to-side. Any banter was initiated by Barlow, who praised Boston’s college-radio scene and joked with the full house of 450, “It’s kinda like a real show. C’mon!”

Even Murph has trouble accounting for the band’s drama-free reunion. “It’s hard for us to answer questions like that. We’re not the kind of band to analyze ourselves too much. It’s partly chemistry. J drums and writes his songs with Lou and me in mind. We have a formula that works.”

Barlow sees it as “a practical move on J’s part. We’re all 20 years older, and there’s a lot of water under the bridge. And at the end of the last tour, it became apparent we needed to learn new songs and write a new record.”

The usually reticent Mascis agrees, and he cites an epiphany of sorts. “I kind of like playing more now than I ever have. Not sure why. I remember talking to Sonic Youth when I was younger, and Thurston Moore said he really liked playing and I was perplexed by it. Now, I understand it. I don’t know if I ever enjoyed anything before . . . ”

At 41, Mascis is still a grumbling, growling singer, and Dino’s trademark snarling guitar hooks and pummeling bass-and-drums are right up front. In nine weeks, Beyond has sold upward of 50,000 copies worldwide. What’s most surprising is how willing the often diffident Mascis seems to play ball. Before the show, with fans lining the sidewalk, he joined Barlow and Murph on JFK Street to pose for photos with a customized purple Yaris. He even admitted, “We’re probably closer to friends than we’ve ever been.”

Barlow went so far as to say of the reunion, “I don’t see an end to it. But that doesn’t mean anything. I’m not looking that far into the future. I’m just pleased we have an album out, and I’m surprised by the reaction to it.”