Six albums deep into Jason Isbell’s solo career, his peers and critics alike are running out of positive superlatives to describe his music. The raw tools were already there when he was penning songs like “Outfit” and “Goddamn Lonely Love” as a member of the Drive-By Truckers; the maturity and sense of his rightful place in the world (musically and otherwise) perhaps was not. In any case, new album The Nashville Sound (Thirty Tigers/Southeastern) should lay to rest for good any lingering doubts about Isbell’s rep as a once-in-a-generation talent, particularly as a songwriter. Besides tapping his able band the 400 Unit (often including Isbell’s wife, fiddler Amanda Shires) to the full extent of their considerable aesthetic capabilities, together ’s ten songs constitute the compelling testimony of a family man of relatively recent vintage reckoning with his responsibilities as a husband, father, citizen, reformed addict and — certainly as far as the realm of roots-rock/Americana is concerned — bellwether. Such a task requires exceptionally broad shoulders, but Isbell emerges unbowed.