The Kills have spent nearly two decades mastering dark moodiness. Here, with just an acoustic guitar and vocals, they manage to pull even more emotion and stark detail from a handful of older tracks. A cover of Rihanna’s “Desperado” is as spare and unsettling as a Hank Williams tune. And hearing both versions of “Echo Home”—its delicately hazy electric take and its sublimely folky do-over—side by side is a study in contrasts.