When first rumored, the pairing of rock god Robert Plant and bluegrass lass Alison Krauss threatened to be a clash of sensibilities.

But last year's Grammy-winning album

Raising Sand

proved otherwise. With the help of producer and bandleader T-Bone Burnett, the two found common ground in eerie, swampy American roots music that mixed blues, early rock-and-roll, and country ballads.

The extroverted Plant and introverted Krauss met halfway on the album, and they did so onstage at the Borgata Sunday night, entering with big smiles from opposite sides as the band kicked into "Rich Woman," the New Orleans hit from the mid-1950s.

What followed was a two-hour, country music-style revue (which will come to the Mann Center for the Performing Arts on July 12), with the two singing in unison sometimes, but with Plant taking the lead for a few songs, then Krauss, then both stepping aside for Burnett to sing a few.

And there was plenty of room to highlight the all-star backing band: Burnett on rhythm guitar; Buddy Miller on lead guitars and electric mandolin (bringing more twang and velocity than did Marc Ribot on the album); Stuart Duncan, whom Krauss called "my favorite musician in the whole world," on banjo, fiddle and mandolin (his close harmonies with Krauss on the country gospel classic "Green Pastures" were highlights). Dennis Crouch on stand-up bass and Jay Bellerose on drums reprised their roles from the album (Bellerose was particularly brilliant driving a spacious, syncopated rhythm on "Fortune Teller," another New Orleans classic).

Although everyone took turns in the spotlight, they formed an ego-less band of restrained virtuosos, including Plant, whose Led Zeppelin persona was all ego (he reportedly turned down a $100 million offer for a Led Zep reunion tour for this one).

Dressed in a flowing red shirt and iridescent burgundy slacks, with his long curly locks and goatee, Plant did some understated hip-shaking and mike stand-swinging, and with his piercing stare and joyful grin, he owned the stage, whether for Townes Van Zandt's cry of existential pain "Nothin' " or for a rave-up romp through the Everly Brothers' "Gone, Gone, Gone."

And yes, they did a few Zeppelin classics: "Rock and Roll" as a slow, sexy ballad, with Plant signaling for the backing "ahh-ahhs" from the sold-out audience that skewed in age closer to Plant's 59 than Krauss' 37; "The Ballad of Evermore" as a mandolin-backed duet; and "Black Country Woman," amped-up and banjo-driven, with Krauss shouting along with Plant.

Those shouts shocked, because Krauss has made a virtue of restraint throughout her career. She looked demure in a backless black blouse and black slacks, and her smiles seemed shy, but her singing and fiddling were anything but: this was a meeting of equals. Her leads on the a cappella "Down to the River to Pray," with Duncan, Plant and Miller doing close harmonies, and on the ancient folk ballad "Mattie Groves" (inserted in the middle of Plant's "In the Mood") were highlights.

After a hand-clapping romp through the gospel classic "You Don't Knock" and a loose and joyful version of George Jones' "One Woman Man," the encore ended with its most beautiful moment: Krauss singing lead with Plant in subtle harmony on the sad valedictory ballad "Long Journey Home."

Sharon Little, who got her start at Ardmore's MilkBoy Cafe, opened with a set of bluesy rock and R&B. She's got a great voice (and a giggly speaking style), but she was bound to pale compared with the vocalists that followed her.