Though she's been around since 1999, "Back to Basics" is only Christina Aguilera [ tickets ]'s third proper album. Playing catch-up, then, the singer delivers a double shot containing more than 20 tracks, the best of which take their inspiration from the burlesque and cabaret shows of the roaring '20s and '30s, the worst of which sound like dumpy, Simon Cowell-endorsed pop hysteria.

Practically a concept album, "Back to Basics" captures several sides of Aguilera, who plays executive producer on the effort. Each track is a modern-day shout-out to the legends that helped write America's songbook--and shape Aguilera's vocal style. "Back In the Day" even finds the singer saluting Otis Redding, Aretha Franklin, John Coltrane (?!?) and Etta James by name. But "Back to Basics" suffers from a poor song sequence that gives it an overly ambitious, unfocused feel.

Aguilera is a devout, reborn Christian on "Makes Me Wanna Pray." She is a devoted partner on "Ain't No Other Man." And with disc-one closer "Thank You (Dedication to Fans)," Aguilera is a gushing, thankful pop star. "You've always been there / To give me that extra love to pull me through." Yech.

But it doesn't take long for Aguilera to relapse into the sex-crazed, R-rated hottie we all know and love. "I still got the nasty in me," she purrs, "Still got that dirty degree," from the buoyant "Still Dirrty." And it's on disc two, produced and co-written with Linda Perry, that Aguilera's nasty side really shines.

"Candyman" is a tawdry take on The Andrews' Sisters' "Boogie Woogie Bugle Boy," with such gloriously lascivious lines as "He's a one stop shop / Makes the panties drop." Later, on "Nasty Naughty Boy," Aguilera gets downright sinful: "I'm gonna give you a taste / Of the sugar below my waist." Hello! Of course, this being a 21st Century pop album, there are also plenty of G-rated moments, including meditations on love lost, her Mama's support, and Aguilera's appreciation for life, and the importance of dignity and self-respect.

It all begs the question: "Why not pick a persona and stick with it?"

Indeed, it's the grown-up, campy, pre-swing stuff on "Back to Basics" that make it such a fun, surprising release. Replete with crackling-vinyl sound effects, classic arrangements and out-of-date studio trickery, this sepia-toned album is more rewarding than anything Aguilera or her peers have done in a long time.

If she'd only shed those clichéd Mickey Mouse pop songs, Christina Aguilera might actually fulfill her dream of becoming an artist with something interesting to say. With "Back to Basics," she is halfway there.