He was obsessed with traditional country music before he was known as Elvis Costello. In the mid-’70s, young Declan MacManus discovered the genre indirectly, through his interest in seminal country/bluegrass-influenced groups like the Byrds, the Band, and yes, even the Grateful Dead. The English pub rock he later co-opted and infused with his unique brand of vitriol had its roots in country as well. Elvis was writing credible country tunes as early as 1978’s “Stranger in the House” and traveled to Nashville to record an entire album of covers, 1981’s Almost Blue. Nearly three decades later, he returned, teaming up with longtime collaborator T Bone Burnett for Secret, Profane & Sugarcane, a 13-track collection of acoustic songs released in June that will make up the bulk of tonight’s set. With backing from the Sugarcanes, a string band comprised of Nashville’s top veteran session men, the stripped-down, rootsy music includes numbers written with and for Loretta Lynn, two originally written for Johnny Cash, and brings to mind 1986’s King of America, also produced by Burnett. If you go, don’t expect anything like the Attractions or the Imposters—it’s not supposed to rock. And wish Elvis a happy birthday; the onetime “angry young man” turns 55 two days after this show. All ages. Sun., Aug. 23, 7 p.m., 2009