Multi-Grammy Award-winning songwriter, producer, and artist Finneas mentored the finalists who were also grouped to perform two of his songs, "Break My Heart Again" and "What They'll Say About Us."
Chayce Beckham opened the show performing Zac Brown Band's "Colder Weather" for his personal idol song.
"You were born on American Idol," Katy Perry said. "You own this stage now. You live here."
He followed up later in the show with his first song "23," which Katy Perry mentioned is number one on the country charts. He also covered Chris Stapleton's "You Should Probably Leave."
MORE | SoCal's Chayce Beckham is the 'Idol' underdog, Katy Perry says
The 16-year-old singer from Florida teared up following her mentoring session with Finneas. She sang "wish u were gay" by his sister, Billie Eilish.
"That was crushed," Luke Bryan said. "You just crushed every aspect of that whole thing. That was your best."
Bishop left the judges speechless with her cover of Motley Crue's "Livewire," which she also sang during her audition.
"Wow! What was that?!" Lionel Richie exclaimed.
Casey also performed her single, "Love Me, Leave Me."
Grace Kinstler awed the judges with her rendition of Kelly Clarkson's song from the first Idol, "A Moment Like This."
"It's always a pleasure when you grace us with your voice," Katy Perry said. "You are a lot like Kelly Clarkson and she's a bonafide megastar."
Later in the show, she performed her single "Love Somebody" followed by Demi Lovato's "Father."
"Glory" by John Legend was the personal idol song performed by Willie Spence.
Katy Perry called it a "spiritual" performance.
The 21-year-old Georgia native returned to perform his first single "Never Be Alone" and closed out with Beyonce's "I Was Here."
"You are a giant of voice," Lionel Richie said.
Willie and Grace also performed Finneas' "What They'll Say About Us" as their duet, while Casey and Chayce partnered for "Break My Heart Again."
In addition to mentoring, Finneas also took to the Idol stage to perform "Till Forever Falls Apart" with friend, collaborator, and acclaimed singer/songwriter Ashe.
Judge Luke Bryan also performed his new song, "Waves."
After the nationwide vote, the top 3 chosen to compete in the season finale are:
Casey Bishop was eliminated.
"American Idol" is ready to crown its winner on a special three-hour live coast-to-coast season finale event airing next Sunday starting at 8:00 p.m.
The top three finalists will each take the stage one last time to perform in hopes of securing America's vote and, ultimately, become this season's winner.
In addition to the finalists, Idol's all-star celebrity judges Luke Bryan, Katy Perry and Lionel Richie will each perform a hit song during the show. Plus, the rest of the top nine return to join renowned music artists Lindsey Buckingham, Alessia Cara, Luke Combs, Sheryl Crow, Fall Out Boy, Mickey Guyton, Chaka Khan, Leona Lewis and Macklemore on the Idol stage for unforgettable performances throughout the show.
Voting for the next "American Idol" starts at the beginning of the episode and will be open throughout the live show.
The search for next season's Idol has already begun. Visit AmericanIdol.com/auditions to learn more.
You can see every performance on American Idol's YouTube channel and watch the full episodes anytime on Hulu.