With its sinister guitar and vocal effects, “No Quarter” ranks among the most ominous and inscrutable songs in the Led Zeppelin catalog. Which likely explains why the members of the ominous, inscrutable band Tool chose to cover “No Quarter” as the opening salvo in their sold-out concert Sunday at New Orleans’ Smoothie King Center.

Tool is more popular than ever, despite having gone 10 years and counting with no new album. In fact, it has released only four full-length albums in a quarter-century. The musicians’ outside projects, their creative perfectionism and, in recent years, a long-running lawsuit have all factored into the long delays between albums.

No matter. Tool, like Metallica, no longer needs new material to fill concert halls. The band’s repertoire and reputation are enough. All 14,000 or so tickets for the New Orleans show were snapped up well in advance.

Tool did nothing to diminish its reputation during the final show of a monthlong tour. For nearly two hours, the quartet served up exactly what fans have come to expect: intricate, precision art-metal cloaked in unsettling visuals and frontman Maynard James Keenan’s unrelenting sarcasm and practiced obfuscation.

Drummer Danny Carey, bassist Justin Chancellor — both of whom sat in for the final song of opening act Primus’ set — and guitarist Adam Jones rendered “No Quarter” mostly as an instrumental. The song’s dark heart beat through their modifications.

Keenan was more of a presence on the second song, “The Grudge.” As has been his custom in recent years, he spent the whole show on a platform to the right of Carey’s drum riser. He was largely invisible in the shadows; by design, the spotlight never found him. Occasionally, he appeared against the backdrop video wall as a silhouette, hunched over, pacing or stomping a single leg, sometimes all at once.

Over the years, he has sported an array of bizarre costumes onstage. He spent most of Sunday’s show in what appeared to be a SWAT team member’s black armor, complete with shin guards, helmet and dark sunglasses. His only utterance for the first chunk of the show was a deadpan, “Smells like New Orleans.”

Tool went about its collective business in a business-like manner. Chancellor’s crisp picking signaled the arrival of “Schism.” As he urged the audience to roar its approval — the bassist was the most animated of the four onstage — Jones and Carey bore into the song’s brawny core as Keenan wailed, “I know the pieces fit, ’cause I watched them fall away.” Decay, emotional and otherwise, is a frequent Tool theme.

Behind the musicians on a giant video wall and side screens, vibrant geometric patterns gave way to the sort of creepy, stop-motion animation pioneered in Tool videos. Alien humanoids did alien things. Creatures were dissected or expelled a dark goo in a perfect circle.

From the shadows, Keenan riffed his own skewed take on the Carnival season. Not the type of guy “that goes to things like Mardi Gras,” he said, he “needed some information. You do a thing and you get some beads?”

He tossed a strand into the audience. “I’ve been led astray, and violated in a way. You don’t want to hear what I had to do to get these,” he said.

New Orleans, he continued, tongue firmly in cheek, is guilty of “ruining my innocence.” Hardly.

As the set list moved through “Opiate,” “Ænima,” “Descending” and “Jambi,” Jones tore off great slabs of electric guitar, Carey powered through fills and tricky time signatures like a more muscular if less finessed Neil Peart, and Chancellor worked especially elastic bass lines. A double-kick drum exclamation point stamped on the end of “Forty-Six & 2” signaled the close of the regular set.

With that, Keenan disappeared; his three bandmates stood motionless for a moment, then left as well. The word “Intermission” appeared onscreen, along with a digital clock counting down 12 minutes. “Intermission” generally implies the midway point of a show. But this was, as it turned out, just a longer version of the standard pause before the encore.

Carey returned to the stage alone. After generating electronic noise on a sampler for a few moments, he embarked on five minutes of controlled soloing. Keenan materialized in a new ensemble that was his version of a Mardi Gras costume: a frilly black tutu with a witch doctor’s mask and top hat. “If you can’t beat ’em, join ’em.” he said.

“Sweat” gave way to the brute force of early Tool favorite “Stinkfist.” Carey, Chancellor and Jones lingered onstage for a long goodbye with worshipful fans. Keenan, in his tutu, had already made his escape.

Follow Keith Spera on Twitter, @KeithSpera.