Murph, J. Mascis and Lou Barlow make up Dinosaur Jr.: Brantley Gutierrez

Bands don’t break up the way they once did. These days, the indefinite hiatus is the popular way of pulling the plug on a group. Take Sonic Youth’s recent split, which guitarist/singer Lee Ranaldo described as the band “ending for a while.” The demise of the original Dinosaur Jr. was so combustible as to have its own lore, including the oft-circulated tale in which frontman J. Mascis clobbered bassist Lou Barlow over the head with his guitar in the middle of a show in Connecticut. Barlow’s ouster also was comical: Mascis told him the band was breaking up when, in actuality, he’d hired a replacement.

“If I was a fan of Dinosaur, I would think that was hilarious,” Barlow told me years ago of the story. Rather than laugh after his ouster from the band, he proceeded to write and sing hateful songs about his ex-bandmate.

“I left that band when I was 21,” he said. “Now it’s just funny how pathetic we were. The years following that, it was a little painful, and I was very angry. But after reading that book (Michael Azerad’s “Our Band Could Be Your Life”) and realizing how absurd and uptight we were, and ultimately how sad the whole experience was, it’s just much more entertaining to me now. And it’s really rare that you get to read such an ugly, ugly story about a band. And I’ve always loved that, when you get to read just the real dirt on a band that you like. So I’m happy that I was able, in some way, to give that to Dinosaur fans.”

If the method of band breakups has changed, the rudiments of reunion tend to be static, which is to say they tend to happen because of money, nostalgia or a combination of the two. These are understandable reasons to reunite a band — especially because there is more money to be made today through touring than selling old albums. Also, many bands from the ’80s underground didn’t make much coin for their work.

Unfinished business is a third cause for a reunion, and the rarest of the three.

The first rule of a reunion should be “do no harm,” which is why the Pixies and the Police reunions have been satisfying and safe. The bands play much-loved songs well and collect a formidable paycheck. The flip of the Pixies is Jane’s Addiction, which has released two junker albums in the nine years since it reunited. Jane’s released just two great studio albums during its heyday. So the percentage of its discography that is well regarded has been diminished by half.

Remarkably, Dinosaur Jr.’s Mascis, Barlow and drummer Murph (just Murph) reconvened in 2005. More remarkable, the band’s reputation has been undiminished in the seven years since, despite the release of three albums of new material. Dinosaur Jr. is the rare reconvened band that has managed to make new music as good or better post-reconciliation than that of its early days.

The early allure of Dinosaur Jr. is still in place, namely Mascis’ guitar leads, which still have a rocket-fueled sense of propulsion. There’s a little more stylistic variance on “Beyond” (2007), “Farm” (2009) and the brand new “I Bet on Sky.” And also a comfort with nuance: The older, wiser Dinosaur Jr. let up on the gas pedal on songs such as “Plans” and “Stick a Toe In,” which offer contrast and texture to the harder-driving tunes. Check out Mascis’ acoustic “Several Shades of Why” from last year for some of his most sublime music. His laconic whining voice, which sometimes battled with the tempo of early Dinosaur songs, pours through them now.

The band is two years shy of its 30th anniversary and showing no signs of subsequent extinction. And to the credit of its three players, Dinosaur Jr.’s new songs don’t send fans tracking to the restroom.

Dinosaur Jr.with Shearwater

When: 8 p.m. Friday

Where: Fitzgerald’s, 
2706 White Oak Tickets: $20; 713-862-3838 or www.fitzlivemusic.com