EXCLUSIVE: Adam Lambert Opens Up About Kesha's Legal Battle, Returning to the 'American Idol' Stage

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Adam Lambert made his return to American Idol on Thursday, debuting his new single, “Welcome to the Show,” and performing one of the most famous covers from his run on season eight of the singing competition show. Lambert opened up to ET afterward about performing on the Idol stage once again.

“It’s nostalgic. I’ve been back on the show every year since I’ve been off, and so each year it’s something different,” he said. “It’s really nice to come back for the final year with a new single and to reprise ‘Mad World,’ which was really cool.”

WATCH: Adam Lambert Debuts New Single on 'American Idol,' Trent Harmon and La'Porsha Renae Bring the Judges to Tears

Lambert also opened up about Kesha, whom he recently spent time with in Nashville, Tennessee, where the embattled singer accepted the Visibility Award at the 21st Annual Human Rights Campaign Nashville Equality Dinner earlier this month.

“From what I know, she's doing really well,” Lambert said. “We go way back from when we first both got signed so it was really nice to see her.”

WATCH: Kesha Thanks Her Supporters, Tears Up While Talking About Personal Drama at LGBT Event in Nashville

Lambert’s not the only former Idol fave to return to the singing competition this year. Kelly Clarkson brought the house down in February with an emotional performance of her single “Piece by Piece,” which brought even the judges to tears.

“I was really touched by her performance,” Lambert gushed. “It was so honest, and I think that’s what hit everybody in the heart. She’s such a talented singer.”

“As a fan of the show, I watched it from the beginning, before auditioning,” he added. “Kelly’s in all of our hearts. She’s an incredible artist.”

WATCH: Kelly Clarkson Brings 'American Idol' Judges to Tears With Emotional Performance of 'Piece by Piece'