In 1997, the three Hanson brothers from Oklahoma were are the forefront of a wave of youth pop that reshaped the music industry. Their debut album "Middle of Nowhere," and its catchy hit, "MMMBop," paved the way for the Backstreet Boys, 'N Sync, 98 Degrees and all the other boy acts that have since pounced on the free-spending teen market.

But the mega-selling groups that followed Hanson are pinups of a different stripe, and in 2000, youth pop is defined by slick harmonies and flashy choreography. The music is layered dance-pop and the concerts and music videos are about as austere as a James Bond film. The Backstreeters and 'N Sync are called "boy bands," but they don't play instruments and they carefully write their songs.

And Hanson? The brothers' upcoming album on Island/Def Jam. "This Time Around," is rock-leaning pop, with their trademark sugary vocals leavened by a healthy dose of guitars. They don't dance onstage because they're busy playing instruments. And instead of enlisting a platoon of Swedish producers and writers, these guys huddle around the house and pen their own lyrics.

They also co-produced the new album.

The question is whether those differences are a strength for Hanson or simply a recipe for becoming the pop world's youngest antiques.

"Things are dramatically different; [it has] changed a lot in the past three years," says oldest brother Isaac Hanson, a music industry veteran at the ripe old age of 19. "We don't know what to expect. It's also very true that it's hard to have a career these days. It's a very fickle market."

The blond brothers -- the other two are 18-year-old (really 17) Taylor and 15-year-old (really 14)Zac -- have changed since they stepped away from the spotlight two years ago, and not just by growing taller. "Their new clothes and hairstyles suggest a bid to be seen as a bit edgier, and their handlers hope the time away might diffuse some of the backlash that greeted their cherubic images after "MMMBop" hit No. 1 in 27 countries.

"Most people only heard "MMMBop," not the whole album, and a lot of them didn't listen to the words, because, you know, it's a really serious song," Zac says in a tone that is more reflective than defensive. "This album is much harder than "MMMBop." It's an evolution of our sound."

In informal market testing, Island/Def Jam reportedly played some of the new songs for listeners without telling them who was performing, which may suggest a degree of hope that Hanson can build on its past success and escape it. Sure, "MMMBop" was named the best single of 1997 in the Village Voice poll of the nation's music critics, but the group was also routinely roasted by comedians and rock musicians as unchewable bubble gum.

Hanson's music was also so of-the-mooment that many industry observers were quick to announce the group's time was done, especially after its "Live From Albertane" concert collection tanked in 1998.

The group itself has taken other steps to change its image with some intriguing partnerships, such as gigs in New York with Grateful Dead member Bob Weir and its new Internet venture with David Bowie's UltraStar company.

"That was cool, jamming with Bob," Zac says. "Really cool."

The lead single from the album, the title track, hit the radio in February. The album arrives May 9, MTV is gearing to give the band a lot of exposure, a promising sign because the network is perhaps the most powerful taste-maker for young fans.

"The fact that they got haircuts or changed their look, that's not as important as the fact that it's a strong record and the single is a strong single," says Tom Calderone, MTV's senior vice president of music and talent. "They always wrote great rock-pop songs, and these are a little more rock."

Taylor says the new sound is a reflection of the brothers' changing musical tastes, which include Beck, Train, Red Hot Chili Peppers and "Sheryl Crow, the Counting Crows, the Black Crowes -- all of the crows."

The album finds its edge in the rootsy guitars -- especially on three tracks featuring another youthful star, blues player Jonny Lang -- but also has softer moments with keyboards and a gospel choir. John Popper of Blues Traveler and DJ Swamp from Beck's band also make guest turns.

Without the glossy, prefabricated vibe that surrounds most of today's youth pop acts, Hanson is "self-contained, very inner-directed," syas Danny Godlberg, ex-chief of Mercury Records, Hanson's former label.

"They were not people who had any type of real grasp of the context they were in," says Goldberg, who now runs the independent label Artemis. "When we did their first video, we couldn't find the language to talk to them with because they had never watched MTV ... They were counterintuitive to pop, which is often this manufactured, calculated genre."

Indeed, today's pop seems to involve more calculations than a shuttle launch. The Hanson brothers' first success came at a time when youth pop was off the radar, but can they repeat it in a scene cluttered with MTV-ready cute guys?

"It's hard to tell," Goldberg says. "The pie's a lot bigger now, but there are also a lot more competitors."