A rock legend who's never been content to rest on his laurels, Robert Plant has continued to seek out adventure and creativity in music. Last month he turned 70, but Saturday night at ACL Live with his band the Sensational Space Shifters, Plant reveled in songs both old and new with the spirit of a performer who still loves what he does, and is grateful for it.

Beginning a three-night stand at the venue (a few tickets are still available for Monday), Plant played a 90-minute set that drew from his Led Zeppelin past but never was wedded to it. The crowd delighted when he pulled out Zep touchstones such as "Black Dog" and "Babe I'm Gonna Leave You," and an exquisite early-set rendition of "The Rain Song" served as a reminder that some of the notoriously heavy band's best moments were quieter ones.

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But the set's first three songs came from "Carry Fire" and "Lullaby and the Ceaseless Roar," Plant's two recent albums with the Sensational Space Shifters. Fresh material from storied rockers often is greeted with skepticism, as Plant seemed to acknowledge when he pulled out another new one in the encore. "Stick with us," he requested. The reward was "Dance With You Tonight," an absolutely lovely tune from "Carry Fire" that's different from anything Plant has ever recorded, almost in the vein of late-period Roy Orbison.

Other highlights included Lead Belly's "Gallows Pole," which Plant prefaced by acknowledged how much a young Led Zeppelin was influenced by traditional American music forms; and the main-set closer "Ramble On," a track from "Led Zeppelin II" that adapts perfectly to the Space Shifters' instrumental range and talent. Indeed, Plant repeatedly gave his fellow musicians the spotlight. Liam "Skin" Tyson's acoustic guitar interludes in "The Rain Song" and "Babe I'm Gonna Leave You" were mesmerizing, while his stage-left counterpart Justin Adams blazed through an electric solo on Bukka White's "Fixin' to Die." Keyboardist John Baggott, bassist Billy Fuller, fiddler Seth Lakeman and drummer John Blease offered stellar support throughout.

Saturday's set differed enough from shows earlier in the week in Dallas and Lubbock to suggest that those attending the Sunday and Monday songs may well get some different material. Plant's repertoire runs too deep, and his personality is too resistant to rote repeats, to expect he'll trot out the same set. If you don't get "The Rain Song," you might get "Going to California," or "Whole Lotta Love." Whatever he chooses, if it's anything like Saturday's performance, it'll be a just reward.

Both Plant and opening act Lucinda Williams have had stretches of living in Austin (at different times), so there's a fitting kinship to this double bill. Williams set the tone for her hourlong set by opening with "Protection," a song from 2014's "Down Where the Spirit Meets the Bone" in which she seeks "protection from the enemy of righteousness." Long a fearless and outspoken songwriter, Williams played to the spirit of an evening where, on the other side of Lady Bird Lake, Willie Nelson and other musicians were rallying to support progressive U.S. Senate candidate Beto O'Rourke.

After touching on other favorites from her long career such as "Changed the Locks" (recorded by the late Tom Petty) and "Drunken Angel" — written for the late Blaze Foley, suddenly a star again thanks to Ethan Hawke's new biopic about his life — Williams drove the sociopolitical statement home with "Foolishness." "I don't need racism/sexism/hate/walls in my life," she sang in successive lines, asking instead for "freedom, hope, peace and love." Across the river, more than 50,000 strong at the Auditorium Shores rally no doubt would have sung along.

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(Update: The Auditorium Shores crowd size has been updated in this story.)