Some concerts simply do justice to the artist's work, but others achieve transcendence. Robert Plant and Alison Krauss, performing a hastily arranged benefit concert for Hurricane Ike victims that attracted an unconditionally loving capacity crowd Friday night at the Zoo Amphitheatre, found that extraordinary place where the event becomes more than anyone could have hoped. It was the summit of the "golden god" and the bluegrass goddess, and the two singers achieved an uncommon alchemy. Plant and Krauss' "Raising Sand" disc was the jumping off point, providing the set's stylistic framework of smoky, after-midnight mood music, but the duo's powerful set extended well into Krauss' classic bluegrass repertoire, the deeper elements of Led Zeppelin and Plant's classic solo work. And by the time Krauss and Plant launched into Zeppelin's "Ballad of Evermore," any subdued, pops concert behavior from the crowd was replaced by a kind of rapture. People were losing their minds, screaming as if it were the mid-'70s and Plant was still the Dionysian rock conqueror instead of the leonine elder statesman holding court with Krauss, whose crystalline voice was in perfect form throughout. Beginning with "Rich Woman" from "Raising Sand," the two singers' voices blended beautifully as bandleader T-Bone Burnett powered the band through the set and drummer Jay Bellerose beat his kit mercilessly with timpani mallets. Burnett has crafted a swamp-rock sound that finds the sweet spot between Plant's otherworldly wail and Krauss' rural sweetness, and while it works beautifully on record, the live experience is a whole other animal. This was especially true when Krauss executed a flawless reading of Sam Phillips' "Sister Rosetta Goes Before Us," with Plant, who until recently was unaccustomed to singing background harmony, giving perfect support in the shadows, or when they came together for a surprising, down-home rendition of Plant's synth-heavy early '80s hit, "In the Mood." The audience seemed equally rapt by new songs such as "Fortune Teller" and Zeppelin favorites such as "Black Dog" or their astounding version of "Black Country Woman." Plant still sounded like the great howler of yore — it didn't matter that it was roots-music great Buddy Miller pulling the strings instead of Jimmy Page. He was in his element, and the nearly constant smile on his weathered face told the tale. There were hints long ago that Plant could go this route, like when he performed Doc Pomus' "Little Sister" with Rockpile in 1979 at the Concert for Kampuchea. While there is always a certain hope that Led Zeppelin will rise again for a full-scale tour, his current pairing with Krauss is clearly a labor of love, and an appreciative Oklahoma City audience returned that love in full.