Exclusive Photos: Carrie, Luke, Blake and More Behind the Scenes at 'Forever Country'
"This project embodies what country music is about," says Bryan, the CMA's reigning entertainer of the year. "We differ as artists, but in the end, we're there for the good of country music and its fan base and its heritage. All these artists that are a part of this have left their mark on the heritage of country music."
"All these songs are timeless classics," says Lambert, who holds a CMA record for the most number of female vocalist trophies, with six wins. "'On the Road Again,' – that's my life and it's a song I grew up with being from Texas."
"When they started saying which artists were going to be on the song, you could see it was going to turn into something really cool so obviously I wanted to be a part of that," says Aldean, a two-time CMA Award winner who remembered "having 'On the Road Again' on a 45 record as a kid" and "playing it on my Snoopy record player."
"I did a duets CD myself a few years ago and I thought 'My gosh, they're putting all these acts together in different times and places, to perform, to sing and to do this mash-up?' " says the singer, a former CMA Awards host, and entertainer of the year winner. "I thought they were absolutely out of their minds! I thought, 'That's going to be more work than they know what they are getting into!' But I think it's a wonderful idea!"
"To think that it's been 50 years, that's quite an accomplishment," Strait has said of the CMA celebration. And he's been a big part of that history: the singer holds the record for most CMA Award wins. He's taken home 23 trophies, the first in 1985 and the most recent, for entertainer of the year, in 2013.
The Dolly Parton classic "I Will Always Love You" "has been a part of my life since I can remember," says McBride, a four-time CMA Awards female vocalist winner. "I sang it in a contest in Kansas and won the chance to come to Nashville for the first time and sing in a national contest here."
"It's been awhile since I've been a part of things like this," says the 78-year-old, who was CMA entertainer of the year in 1972. "But everybody's excited about it. To me, it's similar to when I used to do Hee Haw – you do your part and then they put in what they want of each person. I haven't heard the whole thing, just my own part."
At first, "I really didn't even ask what the songs were – I just said, 'I'd love to be a part of whatever you guys are doing.' You're just honored to be in all of these other artists' company," the five-time CMA Awards male vocalist of the year has said of the project. Told which songs they were working with "I was like, 'What the? How is this going to work?' But I should have known – [producer] Shane McAnally is brilliant."
The two-time CMA Awards male vocalist winner is still recovering his speech after suffering a stroke in 2013, but he makes a special appearance in the video. "Randy and the CMAs just go together," his wife Mary Davis tells PEOPLE. "And it's a real honor for him to be part of this."
"When they first approached me about doing this, I jumped right in," says the native Aussie, who is nominated for CMA entertainer of the year this year. "I sang 'Country Roads' many times over the years, playing in the clubs in Australia and my parents were big John Denver fans. Home is such a universal thing and you don't have to be born in West Virginia to get a sense of what that feels like, metaphorically. That song always resonated with me as being a very warm, organic, familiar feeling of home."
"I've never seen this before in country music where this many people got together for one project," says Underwood, nominated this year for entertainer of the year at the CMA Awards, which she will host with Brad Paisley for the ninth time. The singer says she has a deep connection to all three songs, especially "On the Road Again." "My dad used to take me out on the tractor and I'd sit in his lap and he'd sing that as we'd drive out on the tractor."
"The thing about country music is all those voices are so recognizable. You can tell everybody apart when they start to sing," McGraw, a CMA Awards winner on his own (including entertainer of the year in 2001) as well as with wife Faith Hill (in 1997 for "It's Your Love"), has said of the project. "All the people involved in this are people that we love and people that we loved 10 years ago, 20 years ago … gosh even 30, 40 years ago."