That interplay between adventurous, creative soloing that takes a song in a completely different direction before the precision execution of falling back on the riff or song form echoes the Allman Brothers Band, as does the effortless mixing of the traditional and the contemporary. It’s also there in the way he mixes his own material and songs by others, which he makes his own even while honoring the masters who wrote them, as the Brothers did with “Stormy Monday,” “Trouble No More” and “One Way Out.” Billy does this with a wide range of material, which on Saturday included songs by Townes Van Zandt (“Pancho & Lefty”); Widespread Panic (“All Time Low”); and country and bluegrass pioneers the Delmore Brothers (“Brown’s Ferry Blues” and “Midnight Train”) and Jimmy Martin (“Tennessee”).