With that nimbus of hair spiked by the trademark Afro pick, Questlove, the new Tonight Show bandleader, is never going to be confused with predecessors like Branford Marsalis and Doc Severinsen.

But on a visit home to Philadelphia last weekend, Questlove's father convinced him that maybe this is the job he's always been destined to hold.

"I grew up in a modern vaudevillian environment," says the drummer, whose civilian name is Ahmir Khalib Thompson. Both his parents were singers who took him along when their doo-wop and soul groups toured.

"I grew up with Bowser from ShaNaNa and Dick Clark. I started going to Performing Arts School at 7 and had to play triangle in the orchestra. So by the time I was 18, I knew all these Broadway references," says Questlove, 43.

"At the High School for Creative and Performing Arts, I immersed myself in big band and the All-City Jazz Band," he says. "I was attracted to hip-hop, but I was raised in show biz. This is the job I was raised for. I just didn't know it at the time."

In 1987, when he and Tariq Trotter started the band that became the Roots, they were busking at the intersection of South Street and Passyunk Avenue, with Questlove banging on a bucket.

Their affiliation with Jimmy Fallon, which began when the tyro host took over Late Night in 2009, gave the Roots something they had never had before: discipline.

"Between 1992 and 2009, I'd be surprised if you told me the Roots had rehearsed more than 10 times," says Questlove.

But NBC, convinced a hip-hop band could not have the versatility the late-night format demands, had the Roots on a short leash, reviewing their employment status every 13 weeks.

"We reacted to that guillotine hanging over our heads not in panic mode but by overpreparing," says Questlove. "We rehearse before every show for from three to five hours. I have to say that for each show, we put in a minimum of 10 hours."

He discovered that was not the industry standard when he ran into Will Lee, bass player in Paul Shaffer's CBS Orchestra, on the street. "I asked him, 'What time do you come in for rehearsals on Letterman?' " says Questlove. "He said, 'He's lucky if we come in an hour before the show starts.' "

The Roots stuck to their own schedule, amassing an eclectic repertoire of more than 3,400 songs. Now they're running through all the arrangements again because they just added two horn players from the Dap Kings.

"You can't be The Tonight Show without a horn section," says Questlove.

The band has also written a new Tonight Show theme that will debut Monday night. "It's energetic with jazzy overtones," he says, designed to fit the new opening sequence shot by Spike Lee.

More than any other late-night ensemble in history, the Roots set and amplify the tone for Fallon with their playful, inventive, and surprising musical choices.

Forget "Stump the Band." Questlove and his guys play "Stump the Guest" with their obscure but trenchant walk-on instrumentals. Sometimes you see the flash of recognition hit the celebrity's face, as when Salma Hayek lit up with delight as she realized the mariachi the Roots were playing during her entrance was the theme from a Mexican telenovela she had appeared on 20 years before.

During their first few years as a late-night house band, the musicians would take a tour bus from Philadelphia to New York early in the morning and return at the end of the day.

That soon became wearisome, so Questlove lived in a hotel in Manhattan for a couple of years and now has an apartment. Other band members followed suit, but not all.

"Tuba Gooding Jr., Frank and James - those guys actually moved south to Delaware," says the undisputed beatmaster of late night. "James has to wake up at 5 a.m., drive an hour to Dover, and take the train up here.

"Isn't the object to cut down on the commute?," wonders Questlove. "I asked them, and they said, 'It's only for as long as we're doing this show.' I said, 'You guys realize we're going to be at this gig until we're 60. We're here to stay."

This guy clearly is unacquainted with opening-night jitters. But hum a few bars, and he and the Roots will knock it out of the park.

215-854-4875 @daveondemand_tv