As strong candidates for the ultimate in rock ‘n’ roll longevity, bands such as R.E.M., U2, and the Red Hot Chili Peppers have found ways to persevere into their third decades as working entities in part by being thoroughly embedded in pop culture’s collective subconsciousness. Even an “underground” group such as Sonic Youth, which has never been a steady presence on the radio or television, can be seen as a precursor to a thriving generation of acts that exploded out of its model for moderate financial success and critical adoration.

But don’t forget the Melvins. Forever lurking behind the curtain of mass adulation, the group has remained as prolific and as well-traveled as, say, Willie Nelson. And, no less than the ponytailed Texan, it fully deserves to be revered as an all-American institution. More than 25 years after the band formed in the backwater town of Montesano, Wash. (“Home of the Tree Farm,” the city’s Web site declares), it continues to manifest a highly creative and exacting definition of heavy rock.

The Melvins’ stunningly sludgy tempos, which extracted something like a worldview out of the horror-movie thud of Black Sabbath’s “Iron Man,” underwrote much of what became known as grunge in the early 1990s. But by the time the group’s disciples (most famously Nirvana) had broken through to the mainstream, the Melvins had moved on to recording fastidious, art-damaged concept albums such as “Houdini” and “Stoner Witch” for a major label (Atlantic), reveling all the while in heavy metal’s formal possibilities with a deconstructive, Dadaist glee.

The band hasn’t lost that spirit, even as its most recent disciples, such as the Japanese trio Boris, embellish and improvise on its sonic signature. With their 19th album, “Nude With Boots” (Ipecac), on store shelves this summer, the Melvins have hit the road with founder Buzz Osbourne and longtime drummer Dale Crover, who are performing in the latest of countless iterations of the group. This one features the 2006 additions: drummer Coady Willis and bassist Jarod Warren, both from the Seattle band Big Business. The road will lead the foursome to New York this week for shows at the Music Hall of Williamsburg (tomorrow) and Bowery Ballroom (Thursday).

Like an organism that adapts to survive a changing environment, the Melvins long ago embraced the notion that to stop moving is to die. “It would be ridiculous to do as much as we’ve done if we’d taken a break,” Mr. Osbourne said recently. “This is the life we lead.”

But if the group’s outlook hasn’t changed in 25 years, its music certainly has shifted, if subtly, with the whims of its creators. Unlike some of the Melvins’ more extreme exercises, “Nude With Boots” offers plenty of hooks. “Suicide in Progress” choogles through nearly two minutes of Southern boogie before hitting a dramatic vocal interlude; “Dies Iraea” is the medieval hymn, a staple element of classical repertoire, given a metalized Ennio Morricone treatment; “The Stupid Creep” is a little more than a minute of iron-fisted riffage, vastly amendable to hair-farming, and the title track sounds like a rock hit from the mid-1990s heyday of Pearl Jam or Stone Temple Pilots, with dynamic, chiming guitar sections and anthemic, multitracked vocals that recall the Who. The dual punch of Messrs. Crover and Willis on drums also adds new rhythmic potential to the band’s predominately instrumental songs, which often break into distinct and contrasting sections, like three-and-a-half-minute metal symphonies.

Some listeners have suggested online that the Melvins have, perhaps anachronistically, crafted songs on “Nude With Boots” that are more viable for commercial radio broadcast. This doesn’t sit well with Mr. Osbourne. “What radio station is that?” he asked. “They’re crazy if they think this stuff is radio-friendly. That’s just nonsense.”

Mr. Osbourne, who selected the name “Melvin” in ironic honor of a cash register jockey at the grocery store where he once worked, was emphatic about how difficult it was to create the group’s shuddering walls of sound and crackling eruptions of distortion.

“We’re not really a jammy band,” he said. “It’s all really deliberate. There’s not a lot left to chance. It’s the exact guitar solo that’s meant to be in there. We rehearse a lot.” Onstage, he continued, the musicians work at maintaining the same thoughtfully calibrated mesh as in the studio. “We’re very deliberate. We stick pretty close to the set list, but we go into it as much as possible. It’s not a carbon copy. The songs are not hammered into stone, and I’m not dumb enough to stand in their way.”

Of course, Mr. Osbourne added, it’s impossible to prefabricate an explosive moment. “When the magic happens, you don’t remember it,” he said. “The bad shows are the ones that you remember in vivid color and they feel like they’re never going to end.”

The Melvins perform tomorrow at the Music Hall of Williamsburg (66 N. 6th St., between Wythe and Kent streets, 718-486-5400) and Thursday at the Bowery Ballroom (6 Delancey St., between Chrystie Street and the Bowery, 212-533-2111).