Three years is an eternity in the pop music universe. So the world Hanson was on top of in 1997 is a very different place in 2000.

“There’s more in the rhythmic pop area and the harder rock-rap thing. In the middle there isn’t that much and we fall in there,” youngest Hanson Zac says, calling from a tour stop in San Francisco.

“Rhythmic pop” is Zac’s term for the music made by bands such as ‘N Sync and Backstreet Boys. The success of Hanson’s major-label debut, 1997’s “Middle of Nowhere,” and it’s inescapable single, “MMMbop,” supposedly paved the way for the boy bands’ chart takeover. It’s a connection that doesn’t go over well with the Hansons.

“The main reason we get lumped in there is because of our fan base,” Zac says. “We have lots of teen girl fans, which is fine. They’re great fans, very devoted. But when you listen to the styles of music we are very different from rhythmic pop bands.”

That’s especially true on this year’s “This Time Around,” a harder-rocking disc that features guest appearances by blues guitarist Jonny Lang and Blues Traveler’s John Popper on harmonica.

“It’s really just that we... over three years, did change and came out with something slightly different,” Zac says.

“I enjoy a band that comes out with different music every time,” he continues. “It’s something I’d like to do with all my records -- change it up so that when fans and non-fans hear it they go, “Wow, this is different, I didn’t expect that.’”

The new songs sport rougher edges but aren’t radically different from the ones on “Middle of Nowhere,” One big difference is that the voices of Zac and primary lead singer Taylor have changed in the past three years.

Ironically, the members of the boy bands with whom Hanson is classified mostly are older than the three brothers (Zac is 14, Taylor is 17 and Isaac is 19). Also, unlike those groups, Hanson is a real band, playing its own instruments and writing songs as opposed to working on dance steps.

The brothers became fans of ‘50s and ‘60s rock and R&B through their parents’ record collection. They began performing in 1992 and released two independent CDs and got stacks of rejection notices before signing a contract in 1996.

“We got an amazing opportunity,” Zac says. “There’s a bunch of great bands that nobody knows about. We’re one of the lucky ones that got a break and got to get signed.”

“I think you’re just going out and trying to win new people,” Zac says. “We definitely have people who have stuck around for the long haul, for the whole time. We’ve had people coming up outside venues saying, “I’ve been a fan for three years.’”

Zac believes that the sibling discontent that plagued the Everlys, the Kinks’ Davies and Oasis’ Gallagher brothers won’t hinder the Hansons.

“We’ve always gotten along together really well,” Zac says. “Being brothers, it really doesn’t have anything to do with it. It’s a common love for playing music.”

“There isn’t fighting between us. That would not be good,” says Zac, the beneficiary of a recent growth spurt. “We’re all about the same size. It would be long and painful.”