“As has been the case for many years, the Lonesome River Band headlined the Festival’s first night with a set boasting a musicality both rustic and relaxed. Leader Sammy Shelor again typlified the mix. As an often awarded banjoist, he remains a retiring figure onstage, keeping his solos to a lean minimum in favor of piloting a richly rhythmic ensemble. You heard that with the percolating accessibility of “Thunder and Lighting” and a crisp, set-opening cover of “Ida Red” (the latter a preview of LRB’s forthcoming “Mayhayley’s House” album). But guitarist Brandon Rickman and mandolinist Jesse Smathers, who rotated led vocal chores throughout the performance also deftly decelerated LRB’s propulsion at times, as during the sterling weeper “Mary Ann.” Walter Tunix