Jason Isbell and the 400 Unit make a big noise, as Isbell puts it, and he feels so comfortable letting the band be a main prism through which much of the world hears his art. He can be private but with them behind him he transforms, and there is a version of himself that can only exist in their presence. When he plays a solo show, he is in charge of the entire complicated juggle. On stage with the 400 Unit, he can be a guitar hero when he wants, and a conductor when he wants, and a smiling fan of the majesty of his bandmates when he wants to hang back and listen to the sound