It went down somewhere in Texas. Ben Kenney was on the road with The Roots. In L.A., bassist Dirk Lance had just left Incubus. They wanted Kenney to replace him.

Wandering and pondering led Kenney to a Whole Foods, where he bumped into Tariq Trotter, a.k.a. Black Thought. They rode back to the hotel together and Kenney, figuring the fortuitous meeting was a sign, spilled his guts.

Trotter was completely supportive, recalls Kenney. "[He said,] ŒDo your thing. You wanna go play rock, go.'" Kenney breathed a sigh of relief, made a couple of calls and got on a plane.

"The Roots realize they are a foundation. They understand that if it weren't for them, a lot of shit wouldn't happen." Without them, Kenney'd probably still be playing "Red, Red Wine" in a suburban bar. Philly's hip-hop heavyweights don't seem to mind wearing those big britches. They gave Kenney their blessing even though his departure came just two weeks before the international leg of their tour. More than likely, Trotter and co. are pretty damn proud of the skater kid from Jersey.

But exactly how does one go from playing guitar for a Grammy-winning hip-hop group to playing bass for a platinum hard-rock band? "It was fate," Kenney says without hesitation. "They don't even write scripts like these in the movies."

It was summer 2000. His weekly bass-playing at the popular female open-mic night, Black Lily, went hand-in-hand with jamming with The Roots, but he wasn't a Root quite yet when his card was pulled. Hub, the band's bassist, was temporarily leaving to play for Jaguar Wright. It just happened to be a week before The Roots were leaving for the Area: One tour. Kenney was asked to come aboard and play bass.

Incubus was also on the tour. "The first person I met [from Incubus] was Dirk Lance," remembers Kenney. "I wasn't always an Incubus fan. I'd seen the video with the mustache and stuff, but that was about it."

It was The Roots' job to open for the rock band. "I used to get really jealous. We'd heat everything up, set the stage for Incubus. They'd come out after us and the crowd would just go nuts." After the tour, Kenney continued with The Roots. Hub was back on bass, so he became a guitarist, and as they began recording the Phrenology album, was finally ordained a Root.

But he never lost touch with the Incubus boys. In January he spent a week in L.A. jamming with Jose Pasillas and Mike Einziger from Incubus and Neal Evans from Soulive. That week was the base for a side project called Time-Lapse Consortium, a funk-jazz-infused sound that also includes Suzie Katayama and an 11-piece orchestra.

A few months later, what Kenney and the other Incubus members had been thinking about for years finally happened. "Mike called and told me Lance was out." Kenney heard opportunity knocking on his door loud and clear. The only problem was that damn Phrenology record, the fact that it was doing well and the fact that he was on tour. "I was so freaked out," says Kenney. "I was like, man, I gotta go do this and the guys are gonna be so pissed." There wasn't much time to deliberate. "It became too risky to make Incubus keep waiting. The band had to start rehearsing for Lollapalooza." He left The Roots in Texas.

Since then, Kenney's been a busy dude. There's been a lot of new music written, and of course rehearsals for Lollapalooza. Even though he's never been happier, being on the other side of the country and playing in a completely different genre, Kenney does miss his roots a little. "It's that grass-is-always-greener thing. Turning around and playing rock, I miss things about hip-hop. If I'm playing bass, I miss playing guitar."

Good thing a string of solo and side projects keep him multifaceted. He also hopes to collaborate with his old band again. "I want to play tambourine on the next Roots record." But for now the focus is on Incubus' summer monster tour. Kenney says they'll be playing some of their new favorites, plus all the old stuff. "I'll be learning until I get home in September," he says, chuckling.

Incubus plays the main stage at Lollapalooza, Sun., July 27, 12:30 p.m., $44.50-$59.50, with Jane’s Addiction, Audioslave, Queens of the Stone Age, The Donnas, Jurassic 5 and The Distillers, Tweeter Center, Mickle Blvd. and Riverside Dr., Camden, N.J., 215-336-2000.