The songs Gregg Allman wrote for his solo albums and The Allman Brothers Band occupy the fundament of American music. For all the Allman Brothers’ blues-rock brawn, Gregg seamlessly stitched tender, yearning ballads like “Melissa” into the tapestry of their sound. And Eric Church’s soulful take on the rambunctious “Ain’t Wastin’ Time No More” and Frank Zappa’s volcanic rendering of “Whipping Post” hint at Gregg’s influence on country and rock.