When Willie Nelson and Merle Haggard last got together in a recording studio, it was with their fellow country music veteran Ray Price for the 2007 album "Last of the Breed."
That trio is now down to two, after the death of Price in 2013 at 87, but to hear Nelson and Haggard's latest collaboration, "Django and Jimmie," released Tuesday, you'd think they were a couple of young bucks just getting their feet wet.
The two old-school country outlaws sound downright playful on the album's first single, "It's All Going to Pot," which was written by the album's producer, Buddy Cannon, along with Jamey Johnson and Larry Shell. It not only winks at the country vets' shared fondness for a certain type of smoke but also notes the decline of some attributes of their country.
"I think Willie's sounding like a teenager — he's never sounded better," Haggard, 78, said, relaxing on his tour bus recently at the Stagecoach festival in Indio. "He just knocked me out, made me have to stand up and pay attention."
To Nelson, 82, "It's always fun to hang out and make music with Merle. He's always been one of my favorite singers."
That's the mutual admiration society at work on a high level, given both men are widely regarded as two of the greatest living country songwriters, whose music has shaped the sound of the genre for six decades.
Back when Abbott, Texas-born Nelson was struggling to fit into the Nashville country music establishment of the 1960s, Bakersfield native Haggard and other West Coast mavericks were creating a livelier counterpart to the smooth, urbane sounds that Music City favored at the time. That slickness drove Nelson and fellow Texan Waylon Jennings back to the Lone Star State to do things their way, launching the outlaw movement of the '70s.
"I think 'Okie From Muskogee' might have been the first one I heard him singing," Nelson said in a separate interview as he was getting rolling on a new tour. "I was really liking what I was hearing with Merle, Buck [Owens] and those other guys from Bakersfield. They had a sound of their own and made a great impression on country music."
Likewise, Haggard is a lifelong admirer of Nelson's songwriting, which he said played into the material they chose to work on together for "Django and Jimmie."
"Willie's a great songwriter, and he figures that I'm a great songwriter," Haggard said, "so we're not going to play anything for each other that's not pretty good."
The album strikes a balance with a few new songs, including Haggard's "The Only Man Wilder Than Me" and "Missing Ol' Johnny Cash," an honest but unsentimental ode to their mutual friend. The record also includes three Nelson-Buddy Cannon compositions and a few well-chosen chestnuts from each other's deep catalogs: Nelson's "Family Bible," Haggard's "Swinging Doors" and "Somewhere Between."
Mostly, it's the spirit in their voices that registers on their third album together, dating to 1983's "Pancho & Lefty." Collectively they're singing with more than a century and a half worth of hard-won experience.
"On my  duets album 'To All the Girls…' I'd recorded 'Somewhere Between' with Loretta Lynn before I realized Merle had written it," said Nelson, who in May published his autobiography, "It's a Long Story: My Life," which he wrote with David Ritz. "So we thought we should do that together. He wanted to do 'Family Bible,' which I wrote 50 years ago, and I thought that was great."
The title track comes across as deeply autobiographical, but it was written by Nashville songwriters Jeff Price and Jimmy Melton — with Nelson and Haggard in mind.
"They have both been my musical heroes since I was around 12 years old," Price told The Times. "I've been writing songs in Nashville for 25 years, and this cut is a lifetime musical dream come true."
The song allows Nelson and Haggard to salute two major influences: Gypsy jazz guitarist Django Reinhardt and the man known as the "Father of Country Music," Jimmie Rodgers. The chorus acknowledges their admiration for other key musical figures, including Hank Williams, Lefty Frizzell, Bob Wills, Ernest Tubb and Cash, but concludes that "there might not have been a Merle or a Willie, if not for Django and Jimmie."
"It's a natural for me and Merle," Nelson said. "He's a huge Jimmie Rodgers fans — so am I — and Django is my all-time favorite guitar player…. When I first heard him, I realized I had really been influenced by his music for a long time. I had been into Bob Wills a lot, and in a lot of his songs I could hear Django's style, and that made me realize a lot of us musicians went back to Django."
Added Haggard: "He [Reinhardt] was everything on the guitar that Jimmie Rodgers was with the vocals, and that song 'Django and Jimmie' is really a classic, I think."
As for syncing up harmonies between two of the most idiosyncratic singers in all of pop music, Haggard shrugged off any perceived challenges.
"He's easy to work with," he said. "It may seem [difficult], but I've studied him, and he really has a path, and he knows which side of the beat he's going to land on. Once you realize what he's doing, and he does it twice, you know where he's going.
"Some of the places where he comes in ahead of the beat, you just leave that alone, let him do that. You don't try to put a harmony over it. That's just Willie."