Dionne Warwick and Dolly Parton on Meeting Each Other for the First Time After Decades (Exclusive)

The legendary singers' duet, 'Peace Like a River,' drops Friday.

It's hard to fathom but it's true: Dionne Warwick and Dolly Parton formed a friendship decades ago and, in the years since, have communicated over the phone and via FaceTime, but only recently met in person for the first time.

ET was on the set of Parton's soundstage in Nashville, where Warwick and Parton were filming the music video -- produced and co-directed by Warwick's son, Damon Elliott -- for their duet, "Peace Like a River." The music video and the new track drop Friday.

It came as quite a shock when Warwick answered "right here" after being asked if she remembered the first time they met.

"For me, yeah," Warwick tells ET's Rachel Smith.

"Yeah, 'cause somebody said, how long have you known Dionne?" Parton asked rhetorically.

"We had spent time on the phone. We had done the FaceTime thing and we looked at each other," Warwick continued, "but this is the first time I've had the pleasure to give her a hug."

Parton said she was excited on the ride over to the soundstage with Warwick because, at last, they were able to make this legendary meetup happen.

"I was so excited this morning because when I was riding with you, somebody asked how long have you known Dionne. I said, 'I don't know her, except through her music and I love her music,'" Parton said. "She was always one of my favorites. I had all her records but I don't think I ever met her. I would've remembered had I met her, but this morning, it was like two little young-ins like, 'Hey! Hey! Hey!'"

It's safe to say Warwick and Parton's meeting turned into a mutual admiration society.

"When I met her though, honestly, I knew I wouldn't be disappointed because like she said, we've talked, you know, FaceTime or whatever, they have all that technology stuff we did," Parton added. "But I knew that I would love her because I just felt that voice. It's just kind of inside me. You know that vibe, there's a vibration that you feel when people sing. So I knew I'd love her. And it wasn't like I met a stranger. We just walked up to each other like we've always known each other."

"Dear old friends," Warwick chimed in.

Parton's gospel duet had been years in the making. She tells ET she first wrote the track "in the late '80s" and that "it's a song that stands the test of time."

"It was just a matter of time 'til some wonderful person like Dionne grabbed it and said, 'Let's do this together,'" Parton said.

For Warwick, she feels the project is "preordained" because Parton "had major success with my little cousin, Whitney [Houston], and kept it all in the family. It's that simple."

Warwick, a five-time GRAMMY winner with over 100 million records sold worldwide, said she hopes fans feel inspired by her and Parton's duet.

"This is something that is very dear to my heart, you know, gospel," Warwick said. "I grew up in a gospel family. So, Dolly just touched the right part. She pushed the right button."

Just like Warwick, the Queen of Nashville also grew up in a gospel family. Her grandfather was a preacher. And, just like Warwick, Parton grew up singing in church.

"That's where I learned to sing," said the 10-time GRAMMY winner.

Parton, a member of numerous Hall of Fames, said she wrote the song when she was "going through some things."

"It's always some short-term war," she added. "Whether it's in the family or whether it's in the world or whatever. And I just remember thinking, I just need to feel peace. I just need to flow like a river. I just need to go. So I just started writing the song."

When the music video drops on Friday, fans can expect to feel all the church vibes.

"One of the fun things is we got a choir and we got a band, so we're gonna get to really swaying and singing and really get into the spirit of it," Parton said. "Not just get out there and just doing it 'cause we can, but it's gonna be like we're in church."