While Britney Spears procreates and confides to Matt Lauer that her music is in limbo, her onetime rival Christina Aguilera is burdened by no such distractions or dilemmas. On her third proper album, Xtina asserts herself as the foremost striver of the teen-pop graduating class, now approaching its 10-year reunion. Her nearly two dozen new tracks, spread over two discs, play like a dial-scanning sample of satellite radio: there’s no-scrub hip-hop, adult-alternative folk-blues, small-combo jazz, World War II boogie-woogie, slow jams, hot adult- contemporary weepers and dinosaur-stomp club workouts. Every song is powered by those husky, armor-plated, instantly recognizable pipes.

Basics honors “those who laid it down and paved the way,” so Aguilera name-checks Miles Davis and vintage Marvin and Aretha hits. But Aguilera and her producers (DJ Premier and Linda Perry) haven’t grasped the simple fluidity of old R&B — as opposed to the shrieking choirs, distracting samples and bullying sonic bombast of disc one, produced mostly by Premier. They also don’t seem to know the difference between the sly entreaties of, say, “Let’s Get It On” and clumsy phone-sex come-ons: “Sip upon my champagne”? Many of the lyrics here redefine artlessness.

Labored production isn’t the only problem. (An exception: “Ain’t No Other Man,” where her wrecking-ball voice fights Premier’s whomping beats to a satisfying draw.) Aguilera sings about being on “a spiritual high” now that she’s found love; “The Right Man” even details her wedding day. But she sure doesn’t sound blissed out: Whether taking on Agua-haters in the music biz or reasserting “that freak in me” in spite of her new glam look, she can come off troubled and defensive. It’s a combination that made for some defiant triumphs on her last album, but here it results in joy-challenged music. She sounds more relaxed on disc two’s pre-rock novelties, helmed by Linda Perry, but when a snippet of “Genie in a Bottle” pops up, it’s not hard to yearn for the carefree, pre-Xtina ’90s.

DOWNLOAD: “Ain’t No Other Man,” “Slow Down Baby”