Hannah Harper made her Grand Ole Opry debut in a major career milestone moment, and it was made even more special thanks to a special appearance from Carrie Underwood. Underwood was also performing at the Opry on June 2, and she came onstage during Harper’s set for a special duet.

The women collaborated on Harper’s viral American Idol audition song “String Cheese,” which brought Underwood to tears when she first heard it. The song, which Harper wrote while dealing with postpartum depression, clearly still struck a chord with the American Idol judge, who, as a mother of two, could relate to the sentiment behind the lyrics all too well.

Harper’s Opry performance kicked off an upcoming summer on the road. She’ll be joined by fellow American Idol stars at a pre-CMA Fest performance on June 3 and will then spend the summer and fall touring the country, including opening for Lauren Alaina on several dates of her Stages tour.

After Harper won American Idol last month, she shared a special moment with Underwood, during which she asked her to duet on “String Cheese” in the future. Now, she got her wish!

Auditioning for the show with the original song was a risk that paid off for Harper, as she went viral for the audition and it made her a fan-favorite throughout the remainder of the competition. However, she previously told TV Insider that she was initially warned not to sing “String Cheese” for her first impression performance.

“They told me to prepare backup because the judges don’t love to hear originals,” she revealed. “They want to hear something that they’re familiar with, that they’ve heard before. So I had a backup planned and never had to use it. I was really thankful.”

Harper’s backup was a Jake Worthington song, which she said she was “glad” she didn’t have to use “because no one knew it [anyway]. So it would be the same as singing an original. So I was glad I just went and sang my own song.”