The first time Grammy-winning producer and songwriter Buddy Cannon received a song idea from Willie Nelson via a text message, it shocked him.

The message was the beginning of what became "Roll Me Up," a musical living will of sorts that ended up on Nelson's 2012 album Heroes.

"It's the strangest thing I've ever done as far as writing a song goes," Cannon said over the phone during our CMT.com interview. "But it works. We've got about 25 or 30 songs down, and we wrote them all just like that. We've never sat together in a room or on his bus with a guitar and said, 'Let's write a song.' We talked about doing that, but we both agree that this is too much fun and it works so well, we're afraid we'll mess it up if we try to do it the normal way.

"Usually [Willie] goes to his place in Maui and gets in that mode of life down there," he added. "When he does that, he starts writing stuff and as he writes it, he'll just send it to me. It might be two lines. It might be a whole verse. It might be what ends up being a chorus, and he just sends that to me."

Text was how they started seven songs on Nelson's latest album God's Problem Child, a moving 13-song collection that explores the concept of mortality. They began song eight "Still Not Dead" a couple years ago following a flurry of death rumors and hoaxes that have followed Nelson in recent years.

"[Willie] and I laugh about it," Cannon added. "What can you do? People just say stuff. Maybe somebody heard a rumor that he got sick. Everybody gets sick. Earlier this year, it was rumored that he was on the edge of death. I was talking to him the whole time and he was sick. But he just had this bronchitis."

Jamey Johnson and Tony Joe White wrote the title track, which features the two singers on guest vocals with Leon Russell in one of Russell's final studio performances before his death in November 2016.

"I think all human beings are 'God's Problem Child' pretty much," Cannon said of the title track. "Willie has stated that that title fits him. I know it fits me. I'm sure it fits Jamey and Tony Joe and Leon. It's a hooky, catchy, sounding phrase, and it would apply to anybody who's associated with what is called the outlaw country music, or whatever that is."

Neither Nelson or Cannon artists have any intentions of croaking anytime soon. Willie will ring in his 84th birthday on Saturday (April 29) with a performance at Stagecoach music festival in Indio, California, with his family band. His six-city Outlaw Music Festival with Sheryl Crow, Bob Dylan, Jason Isbell & the 400 Unit, My Morning Jacket and others starts July 1 in New Orleans. The 44th edition of his annual 4th of July Picnic in Austin will feature sets by Crow, Johnson, Kacey Musgraves and more. Details on Farm Aid 2017 are also coming soon.

Not counting his live sets and compilations, Nelson has released more than 110 albums and still pretty much lives on the road, playing more than 100 tour dates a year.

"What makes him such a great interpreter of emotion is the fact that he sings in this rhythmic sense that's different from everybody else," Cannon added. "It's simple. It's really simple but it's not so simple. And the sound of his voice, he has a really unique tone. If you hear Willie singing in an elevator in a real low level, there's no doubt who it is.

"And I think that is the key to his success and the longevity of his career. It's that abstract way of playing and singing that is so unlike anything else that you'll ever hear. There's no genre or boundaries restraining him."