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*Preparations are in full swing for Thursday night’s American Idol grand finale at Los Angeles’ Nokia Theatre where, following Wednesday’s showdown between Kree Harrison and Candice Glover, the entire audience was loaded out and a new one brought in for a pre-tape of Mariah Carey’s performance, according to The Hollywood Reporter.

On deck for the diva, who’ll be joined by exiting judge and longtime collaborator Randy Jackson on bass and a full gospel choir: a medley of her greatest hits, including “Vision of Love,” “Make It Happen,” “We Belong Together,” “My All,” “Hero” and, of course, her new single “#Beautiful.”

According to audience member Ashley Tucker, Carey was dressed in a white mermaid-like gown with feathers adorning the bottom. “She looked like a princess,” the 23-year-old told The Hollywood Reporter, adding that Carey couldn’t take her eyes off a fan’s lamb poster. “Mariah was singing while she was getting her hair fixed and was really cool with the audience,” said Tucker, herself a massive fan of the singer.

And Mariah Carey is not the only judge who’ll be performing a new song on the show. Keith Urban revealed to reporters on Wednesday night that he’s set to take the stage with his latest single, “Little Bit of Everything.”

“It’s a song I came upon and I loved the feeling of it,” said Urban, who added that he would be thrilled to return to “Idol” as a judge next year.

Also set to appear on the finale is South Korean sensation Psy, who’ll be performing the song “Gentleman.” Scheduled duets will include Adam Lambert with Angie Miller, Janelle Arthur with The Band Perry and Franki Valli with the season 12 guys.

Some portions of the show are still coming together, even at the 11th hour. Candice Glover’s duet partner, for example, is still TBD.