There isn't even a firm concept on the album itself, so you'll get Brandi Carlile as a guest on one of Trent's songs, Cleanup Hitter, no guests at all on a cover of Chuck Berry's You Never Can Tell, some classic covers featuring well-known guests and some more obscure one, and more obscure guests. The one overall connection is that they all work well. Indianola (a/k/a Owen Bradley) joins his pal/producer Trent for a slow, dreamy cover of The Hollies' Air That I Breathe, with Hearst's harmonies and a cool banjo line. Matthew Logan Vasquez takes time off from his group Delta Spirit to do a Midwest version of Untitled 1 by Sigur Ros. Americana favourite John Fullbright steps out of character to sing Leonard Cohen's I'm Your Man.
Bigger names include Nicole Atkins on Concrete Blonde's Joey and Rhett Miller singing Do You Love Me Know by The Breeders. Best of them all comes from Hayes Carll, as he and Shovels and Rope completely re-imagine The Clash's Death Or Glory, as a shit-kicking mandolin party tune. You can overthink the value of these things, but when it's a fun listen, that's all that really matters.