Whenever the lead singer/songwriter in a two-person group steps out with a solo album, the first question that comes to mind is whether the musician needed to go out on his own, whether he could possibly be constrained by his lone partner. In the case of Dan Auerbach, the guitarist and singer for the Black Keys, it's not so much that Pat Carney holds him back as that he's such a distinctive, powerful drummer that he colors and changes Auerbach's playing; it's what band chemistry is all about. Opening his own studio, Akron Analog, gave Auerbach an excuse to cut an album without Carney, and 2009'sKeep It Hid is at once completely similar and totally different than the Black Keys. All the same musical touchstones remain -- primarily classic post-WWII blues, often filtered through '60s and early-'70s classic rock -- but without Carney the attack isn't savage, focusing on feel instead of force. To a certain extent, the Black Keys followed that aesthetic on the Danger Mouse-produced 2008 LP Attack & Release, but "Keep It Hid" lacks its studied, self-conscious atmospherics, along with Carney's wallop. Auerbachcompensates by letting everything on "Keep It Hid" breathe -- there's space in his songs and his production, there are ragged edges, room echo, and natural distortion, all making it feel alluringly out of time. It follows that the album boasts more quiet acoustic moments than the Black Keys' records, but the difference is just as evident in songs that are closer to Auerbach's bluesy signature: "I Want Some More" has a thick, swampy rhythm that never quite gets menacing, "Heartbroken, In Disrepair" swirls, and the dramatic build of "When I Left the Room" has an almost psychedelic undertow, "Mean Monsoon" steps cleanly and precisely in contrast to the slow-crawling murk of "Keep It Hid," while the tremendous "My Last Mistake" is the poppiest song Auerbach has ever written. There's variety here, but Keep It Hid never draws attention to Auerbach's eclecticism, especially because it moves along at a rapid clip, never staying in one place too long. It all feels organic, right down to how it feels natural for Auerbach to step outside of the Black Keys to release this album: it really is something that he couldn't have made with Carney, and its existence winds up confirming the immense talents of both musicians.