Ryan Adams has experienced his most consistent artistic success as an acoustic troubadour — but dude always wants to rock. Cheekily billed as a “double-album concept rock opera” about ’80s-vintage junk culture and junkier food, the 21-track III/IV is a self-released outtake appendage to 2007’s Easy Tiger and 2008’s Cardinology. It lands in the same general ballpark as 2003’s new-wave homage Rock N Roll, loose-limbed and manic, with Adams indulging his riff-rock-and-holler side (including one song, “Numbers,” sporting the immortal sing-along chorus, “We’re fucked!”). There’s also room for chiming hooks, goofball scruffiness, and, of course, melancholia. All he wants, Adams sings, is “someone that loves me the way I love Star Wars.” Is that so wrong?