Ketterer has been impressing audiences with his soulful performances for weeks and earned himself Simon Cowell's Golden Buzzer in the audition round of the latest season of the show.
In a recent episode, Cowell gave a shout-out to Brooks, asking him to write a song for Ketterer if he made it to the finals. During Brooks' weekly Facebook Live series Inside Studio G last week, the singer responded.
"I told Simon last week, the opportunity to write, and the opportunity to write for someone else, I haven't done that in a while," he said.
Cowell told Extra last week that it wouldn't exactly be fair for Ketterer to sing a song penned by Brooks during the show's final.
"We've heard from Garth and it's positive. Not that he could write a song for him for the final. That would be unfair," the judge said. "But he does want to work with him. He's being incredible in reaching out to us. Loves Michael. So, fingers crossed."
Ketterer is a pediatric mental health nurse and father of six from Knoxville, Tennessee, and shared that he sees his children in his collaboration with Brooks.
"I am in love with the song that happened," he said. "You know, I really wanted to pass on in the song — I wanted to share my heart as like passing on a legacy, like telling my boys what it's like, what it takes actually to be a man and what it takes to be a man in this day and age and that kind of thing and so yeah, I feel like what happened is beyond what I thought or imagined."
Brooks added, "As a songwriter, thank you. John Martin (and I) got together. He called me up and said, 'Hey, man. Let's write a song for this guy.' And it was really cool, and when me and you talked, we talked about the things you wanted to cover."
"We just tried to write a real lyric from a guy just talking from his heart, so I got to tell you, I'm excited and flattered that you're going to perform it, and I'll be hanging on every word," he said.
In addition to the collaboration, Brooks invited Ketterer to perform at his sold-out concert at Notre Dame Stadium on Oct. 20.
"You come see us, man," Brooks said. "We're going to suit you up with a band. We're going to put you out in front of 85,000 of the sweetest people you've ever played for before, and they're going to be pulling for you, hoss, like no other. This is going to be good."
"I'm going to fall out of this speaker they have me sitting on right now," Ketterer told the singer. "I feel like what happened is beyond what I thought or imagined."
The America's Got Talent finale airs on Wednesday at 8 p.m. ET on NBC.
Photo Credit: Getty / Erika Goldring