VIENNA, Va. – By now, the pairing of Robert Plant, he of legendary rock god immortality, and Alison Krauss, she of bluegrass royalty, no longer seems puzzling.

After 17 years of musical fellowship – give or take a few in between to tend to other projects – these two are simpatico. A pair of musicians who revel in every harmony, appreciate every nuance on fiddle or upright bass and genuinely enjoy sharing the air between them.

At their sold-out show Tuesday at Wolf Trap in northern Virginia, Plant and Krauss met at center stage, briefly touched hands and finger-snapped through “Rich Woman,” the first song on their debut album together, 2007’s Grammy-winning “Raising Sand.”

Backed by an excellent five-piece band including notable guitarist JD McPherson, who also opened the show, and drummer Jay Bellerose, who spent 90 minutes making very difficult drum patterns look effortless, Plant and Krauss captivated during their 16-song set.

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Drawing from “Raising Sand” and 2021’s long-awaited follow-up, “Raise the Roof,” the duo merged vocals over the rootsy guitar and springy, foot-stomping beat of Randy Weeks’ “Can’t Let Go.”

Plant, an onstage fan blowing his mane with true rock star élan, possesses a voice that remains expressive and robust and Krauss, well, to call her singing angelic does a disservice to its beguiling appeal.

A demure presence onstage, Krauss, 52, layered her hypnotic voice over the sultry crawl of The Everly Brothers’ “The Price of Love” while her fiddling added a dose of mournfulness to the fade out of “High and Lonesome.”

While the show fluctuated in pacing, there was no doubting that many in the crowd hoped to rock a little.

Plant obliged – “Want some tempo?” he asked with a grin – and gave a nod to multi-instrumentalist Stuart Duncan, who sawed his fiddle as a replacement for the iconic drum opening of Led Zeppelin’s “Rock and Roll.”

Even as an elder statesman of 75, Plant couldn’t resist swiveling his hips to the “been a long lonely, lonely time” lyric and thrilled the audience further when he hit a bit of a peak-era yowl at song’s end.

Led Zeppelin’s catalog received more of the spotlight than on previous Plant/Krauss outings, with the pair merging unfettered vocals (him) and mesmerizing fiddle (her) on “Please Read the Letter” (technically a Plant/Jimmy Page collaboration) and basking in the Celtic punch given to “Gallows Pole.”

While Plant graciously indulged fans’ desire for Zeppelin songs – even as the authentically rootsy reworkings they’ve become – he was equally interested in the current, praising the “amazing ensemble” of musicians (“I’ve been resurrected!”) and introducing Krauss as “the woman who saved me from the fire.”

A backdrop of mandolin introduced “The Battle of Evermore,” which built to an explosive crescendo of vocalizing. But “When the Levee Breaks,” which the pair recently released in recorded form, brought the main set to a frenetic, soul-gripping close.

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The song’s mystical vibe was punctuated by duel fiddling from Krauss and Duncan, the latter winding into a fury of notes, as Krauss couldn’t help but smile watching him play. Plant, meanwhile, also stepped back in admiration, clapping his hands to a never-ending beat.

The Plant/Krauss run, which started earlier this month, rolls through September, with some dates as part of the Outlaw Music Festival Tour with Bob Dylan and Willie Nelson.

What they’ve crafted together is mostly Americana, a bit rock, some blues and a little bluegrass. It's not only an appealing blend, but undeniably visceral.