For most of Jo-El Sonnier’s five decades of music making — minus part of the time he spent pursuing a country career on Nashville major labels — his medium and his message have perfectly aligned. And the singing accordion player’s primary message is Cajun pride: In fact, that exact phrase emblazons one of about a dozen of the albums he’s made with “Cajun” in the title. He may have recorded Hank Williams’ lighthearted novelty number “Jambalaya,” but the Louisiana native is serious about doing justice to his roots. Country gospel singer-songwriter Buddy Greene is another guy on this bill who’s made albums showcasing his instrumental chops — in his case, on harmonica. Then there are a couple of acts from opposite ends of the bluegrass spectrum: twentysomething acoustic pop band the Farewell Drifters, whose new album Echo Boom will be out next month, and trad-leaning songsmith Larry Cordle, who recently released the old-timey story-song collection Pud Marcum’s Hangin’.