Brett Young was a guest mentor on Sunday's (April 7) episode of American Idoland he also sang with contestants, performing a heartfelt duet of his hit "Mercy" with hopeful Laci Kaye Booth.

Booth was a bit shocked when she found out she'd be working with Young — and a little starstruck. "When I found out that I was working with Brett Young, I was absolutely shocked. I am obsessed with his music," she remarked.

She was also nervous, she explains, to perform without her guitar. The Texas native frequents writer's rounds in her home state, and when she sings in front of a crowd, she always has her guitar with her — her "baby," she says. Young assured her she could perform without it.

"You're comfortable with your guitar cause you've always done it that way," he said. "But I think it's just putting yourself in that position enough times. I think there becomes a point when you're so caught up in the song and connected to it — lost in the song that you forget about that."

Booth ended up singing "Mercy" with Young without her guitar, and didn't appear nervous. The crowd seemed to love her voice, and cheered her on when she began.

Also on Sunday's episode of American Idol, contestant Riley Thompson got the chance to collaborate with Young on his song "Like I Loved You." She was thrilled, especially thinking about how her friends would freak out when they learned that she'd had such an opportunity.

The hopeful told her celebrity duet partner that she loved "Like I Love You" and songs like it — love stories.

"It is a love story it's a tragic love story. It's a painful song with a little bit of anger," he explained.

It was Thompson's first-ever duet, and her first time to sing harmonies, but ultimately she nailed it, with Young comparing her to an all-star country legend. "You killed it, you have such a cool voice — little hints of Dolly there the way it breaks."

Watch Brett Young Sing a Heartfelt "In Case You Didn't Know" for RISERS

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