“Even back when I first met him, when he was dripping with that Southern rock, Skynyrd-is-cool attitude, he had the ability to pull these beautiful songs out of his pocket,” his friend Justin Townes Earle says.

Isbell married Tucker in 2002, and she joined the band as its bassist in 2003. By 2007, the band was in disarray. “We had gotten to the point where we just hated being around each other,” Isbell says. His exit from the band was carefully stage-managed. It was said to be about creative differences among friends, and about Isbell’s desire to go solo because he was writing more songs than the band could handle.

But the reality was more complicated. Hood called Isbell and suggested he take some time off and get his life together. Isbell replied that if the band was going to tour under the name Drive-By Truckers, he wasn’t going to miss even one show. Cooley then called Isbell and said, as Isbell recalls, “that isn’t going to work for us.” He was forced out. “It was heartbreaking,” Isbell says. “I couldn’t picture what I was going to do. But now I can’t picture things having gone differently. I love those guys, but I’m glad I’m not playing with them anymore. I think they’re glad of it, too.”

On a bright afternoon in Nashville, Isbell was standing outside Cobb’s studio again, taking another cigarette break and telling me about the years following his breakup with the Truckers, wincing as he did so. On one occasion he was arrested for public drunkenness. He remembers waking up in strange places with no idea of how he got there.

These days Isbell is a popular and witty presence on Twitter, but in January 2012, a drunken tweet led to a feud with the country singer Dierks Bentley. Isbell claimed that Bentley’s single “Home” sounded too much like “In a Razor Town,” from Isbell’s 2007 album, “Sirens of the Ditch.” Isbell consulted a musicologist, who ultimately absolved Bentley and his co-writers, Dan Wilson and Brett Beavers, of plagiarism; the whole incident would end up costing Isbell a few grand in legal fees.

After that, Shires finally got him into rehab. “She got on the phone and called my mom and called Ryan Adams and called my manager and called a lot of other people whose opinions I respect and told them that I really wanted to do it this time, and to hold me accountable.”

Newly sober, Isbell is looking forward to touring behind “Southeastern” along with his band, the 400 Unit. He was funny talking about the almost-comic indignities that can befall a midlevel performer at large in America circa 2013. He mentioned the gruesomeness of a “pentagram tour.” When I asked what that was, he replied: “It’s when all your shows are spread out geographically, like the points of a star. There’s a lot of driving to do. You get rid of that booking agent real quick.”