TORONTO - Allison Russell is riding an emotional high after she joined several friends and music contemporaries on stage during Joni Mitchell's surprise performance at the Newport Folk Festival. Sunday's concert was the first time the legendary Canadian singer-songwriter played a full live set in more than two decades, while Montreal-raised Russell lent backup vocals and played clarinet. "I'm still levitating," the Juno-winning artist behind "Outside Child" said on the phone from Rhode Island a day after the performance. "With every song you could see her visibly gaining strength and power. She sang her heart out and we all got to bear witness and support it." Mitchell's return to live music set social media on fire Monday morning as fans shared video of the set. The beloved musician appeared as a guest of Grammy-winning artist Brandi Carlile, who was closing this year's edition of the festival with a show billed as "Brandi Carlile & Friends." Instead, it was the 78-year-old Mitchell at centre stage, accompanied by Carlile and other guests, including Wynonna Judd, Marcus Mumford, and Russell. "She was so humble, sort of going into it like, 'I hope I do a good job. I hope I sound good,'" she remembered Mitchell saying. The show opened with the group singing "Carey" before they moved onto other classics, including "Both Sides Now," "Big Yellow Taxi" and "Summertime." Mitchell sat in the middle on a cushioned chair that resembled a throne. The stage design was inspired by so-called "Joni Jams," an invite-only event for musicians who join Mitchell at her Los Angeles home to perform together. "That was Brandi's idea, to make Joni feel as relaxed and comfortable as possible, and give the gift to the Newport attendees that they were joining Joni in her living room," Russell said. "It was such a relaxed atmosphere at the same time, in front of 10,000 of Joni's new best friends." At one point, Mitchell strapped on an electric guitar to play "Just Like This Train," before closing the show with "The Circle Game." The Newport music festival has long embraced Mitchell's presence in folk music. In 1967, when she was still an unknown singer, organizers invited her to appear as part of a lineup of up-and-coming musicians that also included Leonard Cohen. Mitchell has been gradually returning to public life after she suffered a brain aneurysm in 2015. Last December, she was a Kennedy Center honouree in recognition of a lifetime achievement for artistic excellence, while in April, she was toasted as MusiCares' Person of the Year at the Grammys. After Sunday's show, Carlile invited Mitchell, Russell and the other musicians to celebrate over dinner. That gave Russell a chance to chat with her idol about their shared Canadian roots. "Joni had her favourite food, which is lobster," Russell said. "I got to talk to her about Saskatchewan," she added, as Mitchell grew up in Saskatoon. "She was so excited to find out that my family was from there, and our mutual appreciation for the beauty of Saskatchewan, which eludes some people but which we feel deeply." After missing out on a recent edition of Joni Jams due to her busy schedule, Russell is making plans to attend the next one. She said one thing the Newport show proves is that Joni is far from finished being an artist. "It's almost like the world had relegated her to history, but she's very much present," said Russell, who plays the Edmonton Folk Festival on Aug. 6. "Her legacy is not nearly done and she's not nearly done. I think she's coming into a whole new season."