Venue: Greek Theatre, Los Angeles (Monday, June 23)

At first thought, Robert Plant might seem an unlikely outlet for a celebration of Americana. But think about the myriad sounds from the colonies that Led Zeppelin melded into its music, and it makes sense.

His collaboration with bluegrass torchbearer Alison Krauss has produced a platinum album, a Grammy and now a tour that melds a litany of American roots influences into a tasty gumbo. Supported by an ace five-man band including guitarist, producer and project instigator T Bone Burnett, the duo's show Monday at the Greek was a satisfying and poignant amalgam of musical and performance styles.

Plant and Krauss traded off and shared often understated vocals as the band culled sounds both esoteric and familiar. Leading with the record's reverb-drenched, midtempo opener "Rich Woman," the two-hour show skipped across genres with a reverent exuberance.

The crowd, of course, wildly cheered early on when the band sneaked into Zeppelin. But this was a much different "Black Dog" -- a slow, growling, barely leashed blues. Plant's original wail was muzzled into a soft-spoken duet with Krauss that later featured a fiddle solo -- about as far away from Zep land as it could be.

There were a couple of other numbers from Plant's old band -- a peppy reworking of "Black Country Woman" and a take on "The Battle of Evermore" put the Bics to their mind-altering use -- but this show was about the old American songs, and they earned the attention. Plant receded to the back of the stage to offer almost-whispered backing as Krauss' angelic voice enveloped "Sister Rosetta Goes Before Us." As she soloed during the piece, her fiddle was biting then soothing, always affecting.

Krauss stayed at the microphone for "Through the Morning, Through the Night," an ancient-sounding country lament that belies its late-'60s origins. She later offered a haunting take on Tom Waits' "Trampled Rose" then fronted a gospel double of "Green Pastures" and "Down to the River to Pray." The latter -- the lone song from the "O Brother, Where Art Thou?" phenomenon -- was done in compelling a cappella.

Krauss often sang with her hands behind her back, looking reverent or polite, maybe even a bit uncomfortable. As for their unlikely pairing, she and Plant mostly kept their distance, not even making much eye contact. And when they did, it looked more like midteen awkwardness than the flighty and flirty photos on the album sleeve.

Plant was back into the spotlight for "Fortune Teller." Here he seemed to be visited by the spirit of his Zeppelin past -- standing with legs crossed, doing tiny hand claps and doing that mini air guitar thing. But the pace then slowed a bit with "In the Mood," Plant's creaky solo hit that was dull as ever despite the addition of twin fiddles and a snippet of the ancient English folk tune "Maddy Groves."

He saved his most Zeppelin-like vocal for Townes Van Zandt's "Nothin'." In introducing it, he expressed his adoration for American roots music. Maybe it's time to compensate those bluesmen who saw Zeppelin "borrow" from their songs.