Dr. John revives the Night Tripper persona for his new album Tribal, which features guest spots from Derek Trucks, Donald Harrison, and tunes by Bobby Charles and Allen Toussaint.

The album of remixes of Lady Gaga's hits was originally released in Japan.

The fifth studio album from Kelis features producers David Guetta and Benny Benassi, bringing dance and techno tidbits within her soulful R&B mix.

After a three-year hiatus, Macy Gray delivers soulful vocals, storytelling lyrics, and sparkling melodies on her latest album.

Subtlety not being part of Christina Aguilera’s vocabulary, she trades the retro-swing of Back to Basics for the future-pop of Bionic, receiving assists from a roster that reads like a who’s-who of progressive pop in 2010: M.I.A., Le Tigre, Peaches, and John Hill & Switch, known for their work with Santigold. But like the half-cyborg/half-diva illustration of the album cover, this revamp is only partial. Aguilera hedges her bets by adding a ballad from old friend Linda Perry, gets Tricky Stewart to produce a trio of cuts, drafts Polow da Don and Focus… to produce some heavy and slow R&B, respectively, letting enough air into the machines to reassure hesitant fans that she hasn’t abandoned her roots. All this hesitancy means that for as many risks as it takes, Bionic doesn’t feel daring. Apart from the stuttering opener of the title track and glassy chill of “Elastic Love,” notably the two Hill & Switch productions, this never delivers the future shock it promises, but that’s not necessarily a bad thing, because the robot-diva hybrids are often interesting even when they stumble, as they do on “WooHoo,” its incessant title loop piercing like a dental drill. Exhibit A in Xtina’s curious tin ear for sex, “WooHoo” doesn’t work as temptation, not when the chorus come-on is “licky licky yum yum,” but her crassness is no longer alienating as it was on Stripped; it’s simply part of her persona, just like her shameless narcissism, showcased on the closing “Vanity,” where she gets her kid to confirm that she’s the greatest of them all. This triumphant self-possession comes so naturally to Christina that it’s hard not to wish that she acted so boldly throughout Bionic, letting the entirety of the record be as distinctly odd as its best moments. Frankly, the deluxe edition of Bionic does suggest what the album could have been: it’s supplemented by four bonus songs that are wildly imaginative, whether it’s the clattering, chanting “Bobblehead,” the cool synth glide of “Birds of Prey,” the perfect new wave pop of “Monday Morning,” or Sia’s mournful ballad “Stronger Than Ever.” In their place on the album proper are competent, relatively colorless club odes to fashion and fabulousness and Perry’s boring inspirational “Lift Me Up,” songs that play to Aguilera’s persona without inhabiting it. The rest of Bionic -- not just the hipster flirtations and Sia’s trio of richly ruminative AAA ballads, but the tracks directly within Aguilera’s wheelhouse, like Tricky Stewart’s wildly successful, slinky “Desnudate,” and the sultry slow burner “Sex for Breakfast” -- find Christina not playing to expectations but simply acting as a natural diva and is all the more compelling for it. ~ Stephen Thomas Erlewine