Britney enters the torrid zone

If growing up is hard to do, you have to pity poor Britney, who has to do it over and over. At this point she can’t release an album that’s just a bunch of songs. Each record must somehow be a measure of her maturation, like height lines penciled on a door frame. And whenever one comes out, everyone gathers around to see what’s become of the little girl they used to know.

There will be clucking and breast-beating aplenty over the Britney Spears of “In the Zone” (due in stores Tuesday). This full-on sex kitten makes the mild suggestiveness the previous Britney-grows-up album, 2001’s “Britney,” seem downright innocent.

“I don’t wanna be a tease/ Will you undo my zipper please,” she coos in “Showdown,” one of seven songs on the album she co-wrote. R. Kelly, apparently not worried about tainting his jury pool, contributed “Outrageous,” which has Britney apparently stepping out wearing just a trenchcoat and underwear. “Breathe on Me” describes an encounter so quiveringly intense that actual touch would be too much.

None of this comes close to the raunch threshold established by the prurient popsters and rappers who populate the charts these days, but because she arrived as pop’s Rebecca of Sunnybrook Farm, her transformation from teen to tart does carry a little shock.

It also seems less about growing up than about a strategy of scandalizing in the manner of Madonna, who seems to have become Spears’ dominant role model, both musically (one “Zone” song, “Brave New Girl,” sounds like a homage to the electronica Madonna) and in strategic planning -- specifically pushing the public’s buttons to make it pay attention.

Spears is no Madonna, but today’s tabloid-and-technology celebrity machinery is so pervasive and relentless that she might be able to get just as good a ride.

So the Spears-Madonna duet that opens “In the Zone” is more about high-concept pop-culture iconography than any musical vision. But the jittery backing track produced by Redzone makes it hard to resist, and that’s the key to the strongest moments on the album -- vibrant, inventive frames that enhance the sensuality and promote the sex-kitten persona without putting any demands on Spears’ limited voice.

The Atlanta rap duo the Ying-Yang Twins join her on “(I Got That) Boom Boom,” and their raw, unfettered exuberance elicits the loosest, most spontaneous performance Spears has ever recorded. “This is for the Southern boys out there,” she says, cueing the unlikely arrival of a banjo amid the thumping track.

Throughout the album Spears does a game job of keeping up with the beat on rapid-fire rap verses, and she coos and purrs her seductions like an actress overdubbing a soft-core erotic cable TV show.

But she’s still utterly anonymous as a singer. That doesn’t really damage the sexy, peppy tracks (in fact, it might be part of the fun), but it leaves the ballads empty, and “In the Zone” nods off into their sudsy embrace about two-thirds of the way through.

Given her deadpan delivery, she’s most believable when she portrays someone numb and weary. In “Early Mornin’,” a slow, slinky Moby production about how exhausting all this nightclubbing and globetrotting can be, she describes returning to the hotel at dawn and passing out on the couch, and it’s the only time she balances the vitality and conviction of the party songs with any genuine reflection or vulnerability.

That song also suggests a certain joyless compulsion behind all the partying, a theme that might be exploited by an artist who really has grown up and is interested in digging below the surface.

But let’s not begrudge her her fun. She’s young, she’s rich, so why shouldn’t she strike while the iron -- among other things -- is hot?

*

Britney Spears

“In the Zone”

Jive

Rating: **