When guitarist/singer/songwriter Jason Isbell put together his solo debut, Sirens of the Ditch, it was a prolonged process carried out over several years while he was a fulltime member of Drive-By Truckers, those purveyors of raucously rockin’, whiskey-drinkin’ alt-country music.

“I only had a day or two to record it at a time,” Isbell told me during a phone interview a few days before kicking off the second leg of his spring tour with his band The 400 Unit (pictured).

Squeezing solo studio time into an already jam-packed gigging schedule might’ve been easy for your standard hired hand, but Isbell made up a third of DBT’s triple axe attack and was a productive songwriter throughout his six-year tenure with the band. He’d always brought his own distinctive flavor to the Truckers’ sound and as he drew closer to finishing his record, it became clear he was headed down a different path than the rest of his bandmates, both musically and personally. The dissolution of his marriage to DBT bassist Shonna Tucker didn’t make things any easier, so three months before he released Sirens in 2007, Isbell made his amicable exit.

Sirens sounded a lot like a DBT record, and though it was well received by critics and fans alike, there was a lingering curiosity about the direction he’d take with his follow-up. Jason Isbell and The 400 Unit, recorded in Muscle Shoals and released on Lightning Rod Records in February, is a clear departure from the Truckers sound. It’s also more cohesive than his solo debut. Isbell’s pleasantly husky drawl is set against rootsy, Southern-fried rock ’n’ roll with countrified pop melodies and the soulful, gospel-tinged Muscle Shoals sound: tough, passionate, unflinching, melancholy, and sincere.