Amy Grant and Vince Gill Met Through Christmas Music. Now They're Paying It Forward: 'The Gift of Love' (Exclusive)

When Amy Grant and Vince Gill married almost 25 years ago, they never gave a moment’s thought to merging their already long-established careers.

“We had enough of our lives under our belts that we knew we didn’t want to all of a sudden be Donnie and Marie or Sonny and Cher or whoever,” Gill, 67, tells PEOPLE during a joint interview with the couple for this week's issue. “There was no point in that.”

But rest assured that one thing can always make these two singular legends set aside their declarations of career independence: the Christmas spirit.

The couple’s annual holiday residency at Nashville’s historic Ryman Auditorium has become a longstanding tradition not only for local fans but for countless more who travel from all corners for the musical feast. And this year, Grant and Gill are celebrating their Ryman concerts — now numbering over 100 — with their first joint Christmas album, When I Think of Christmas.

The project features two new tracks plus five previous recordings from each artist, including two of Grant’s signature Christmas songs, “Breath of Heaven (Mary’s Song)” and “Tennessee Christmas” (both of which she co-wrote). Gill applies his celestial tenor vocals to standards like “I’ll Be Home for Christmas” and “O Holy Night.”

As a Christian artist first and foremost, Grant, 64, is perhaps more closely associated with Christmas music than Gill, but the couple actually met, in December 1993, when Gill invited Grant to be on his televised holiday show.

“Truth be told, we invited Amy because it was a Christmas show, and we knew she had a pretty big following in that world, so we could use the ratings,” explains Gill, whose trademark wit is never far from the surface.

His wife, sitting by his side, can’t resist teasing back. “You just needed a chick singer!” she ribs.

Gill later traded with Grant, appearing in her seasonal benefit show in Nashville that same year, and the two quickly became friends and occasional collaborators. Each were in first marriages at the time; after their respective divorces, they began dating in 1999 and married in 2000.

The tradition of their live Christmas shows has grown slowly and steadily over the years. They began touring together off and on during the holidays in 2008; six years later, they chose to stay put in Nashville and scheduled six nights of Ryman concerts. Today, that number has doubled, and each year, the shows quickly sell out. (Grant also regularly goes out on tour during the Christmas season with fellow Christian artist Michael W. Smith.)

Though “Amy and Vince” is now almost synonymous with Nashville's holiday music scene, each has a different relationship with the holiday’s sounds.

“Early on, I recorded Christmas music because faith was so comfortable for me to talk about,” says Grant who's long been considered the queen of Christian pop. “Christmas is the one time of year when everybody feels comfortable saying ‘Jesus.’ Faith to me made it so natural to go, ‘Oh, let’s write songs about this.’ So, yeah, it’s the gift of love.”

Gill admits feeling some awkwardness about his holiday reputation. “I think I’m going to leave ‘the king of Christmas’ to Johnny Mathis and Bing Crosby,” says the artist, who planted his hit-making career in country music and is now a member of the rock band, the Eagles. “Do I really love Christmas music? I think it’s okay.” He chuckles at his assessment. “It’s not the Stones, but it’s pretty good.”

What’s kept them returning year after year?

For Grant, the shows are “a beautiful, easy way to celebrate community, family, faith, and hometown, and we all get to do it together.”

Gill says he’s come to realize how many people count on their shows to kindle their Christmas spirit. “It’s part of their tradition,” he says. “It means something to them. It feels really good in your heart to go, hey, people like this. People want to come see it, and people get a lot from it.” He says he also simply enjoys "watching Amy shine and watching people respond to watching her shine."

Over the years, audiences have come to expect certain things during the Ryman shows: Gill’s witty banter and exquisite guitar play, the (cotton) snowball fight that breaks out during “Rockin’ Around the Christmas Tree,” Grant’s crescendo moment singing “Breath of Heaven.”

The couple also traditionally ends the show with a duet of “’Til the Season Comes Round Again,” the heart-tugging ballad that Gill originally recorded for his first Christmas album, in 1993. It's also the final track, as a duet, on When I Think of Christmas.

Grant says she loves sending audiences off with its savor-the-moment message.

“The Christmas shows that we have at the Ryman are just a moment for everybody to take a deep breath, to look around, to acknowledge the gift of each other, the gift of that moment, and yeah,” she says, “that song says it all.”

But the lyrics also offer the promise of next year: “By a warm fire, let's lift our heads high / And be thankful we're here / ’Til this time next year.”

Grant says she takes that message to heart, too — but she doesn’t take it for granted.

“To us, to me,” she says, “every year feels like a gift.”

For more from Amy Grant and Vince Gill, pick up the latest issue of PEOPLE, on newsstands everywhere Friday.