Bluegrass and rock in harmony

Like couples with nothing in common who fall madly in love, RobertPlant and Alison Krauss make beautiful music together. Last nightthe iconic rocker and the bluegrass superstar performed songs fromtheir 2007 album "Raising Sand," a collection of American classicsboth vintage and contemporary, as well as a handful of tunes fromeach artist's solo catalog. Where the album is painstakinglysubdued - a dusky wash of deep tones and muted percussion with narya shimmer or an edge within earshot - the live show was endlesslydynamic.
Plant and Krauss were accompanied by a roots supergroup thatincluded their producer T Bone Burnett (whose dark magic is at theheart of this remarkable collaboration), guitarist Buddy Miller,drummer Jay Bellerose, bassist Dennis Crouch, andmulti-instrumentalist Stuart Duncan.
The pair opened with the swampy, late-night blues of "Rich Woman,"segued into a fiddle-and-mandolin-stoked thigh-slapper in "Leave MyWoman Alone," and proceeded to blow the crowd away with ahauntingly reimagined version of Led Zeppelin's "Black Dog," slowedto a march and configured for banjo and upright bass. Burnett'shandprints were all over the arrangement, but Duncan's JimmyPage-worthy solo - on violin, no less - introduced fans to thesideways sort of heaviness that would color the captivatingtwo-hour set.
Egos were checked at the door. Plant ensconced himself behind amicrophone at the back of the stage to sing back-up while Kraussloosed her piercing, crystalline soprano on the Gene Clark classic"Through the Morning, Through the Night," and he formed aclose-knit harmony trio with Miller and Duncan during Krauss'ssweet, delicate read of the traditional "Down to the River toPray." Plant blended happily into the dusty musical fabric whileshe burrowed into gripping, minimalist covers of Sam Phillips'"Sister Rosetta Goes Before Us" and Tom Waits' "Trampled Rose."
Krauss, who has found a new ferocity (and decibel level) in hercommunion with the rock god, shadowed Plant with equalgraciousness, lending mighty harmonies and almost savage fiddle onmajestic, organic renditions of the Zep gems "Battle of Evermore"and "Black Country Music." The Zeppelin fanatics who figured thiswas the next best thing to the nonexistent reunion tour - and not afew of them peppered the crowd - danced ecstatically.
Burnett took a turn in the spotlight, as well, stepping to themicrophone for rousing takes on his own "The Rat Age" and "BonTemps Rouler."
"We all come from different musical places but this week we lostone of our founding fathers," Plant said before the group launchedinto a raucous cover of Bo Diddley's "Who Do You Love?" Yet overthe course of the evening it became clearer and clearer just howmuch common ground these seemingly disparate musical forces share.It's in their deep affection for the music's roots - the seminalchanges in the Everly Brothers' "Gone Gone Gone (Done Moved On),"and the cosmic mournfulness of Townes Van Zandt's "Nothin." Thelatter materialized as a sinewy incantation: Plant howled like ananimal, with Krauss baying to his right, and the audience respondedin kind.
Joan Anderman can be reached at anderman@globe.com .