Sunday nights outside Tunnel, the line around the block is so long you’d think Puff Daddy was inside, handing out the Benjamins, baby; but all those kids in the Polo and Hilfiger are really waiting to see the guy who helped make Puffy a star. ”Go Flex, go Flex!” says his Alvin and the Chipmunks-like tag on Hot 97 FM, the local radio station that rocketed to No. 1 in the land after Funkmaster Flex took control of the evening show. Flex, the hottest D.J. in America -- the “hardest-working man in hip-hop,” by his own confident account -- is no mere player of records but a music-industry playa, not so different from the bad boy at Bad Boy Records himself. “It’s scary when you see them in the station at the same time on their cell phones,” laughs Dennis Rivera, Flex’s producer and cohost at Hot 97. “They never stop making moves.” Neither of these young hip-hop moguls shows any intention of ceasing to synergize (“I’m always thinking of the next thing to do,” Flex says demurely of his plans); and the real reason behind their success (forget the schmooze factor) may be an uncanny sense of what makes a body move. “Flex can make a gold album and cold rock a party,” says Puffy. One young man, pumping arms to keep warm outside Tunnel, puts it this way: “I’m gonna sweat my ass off tonight.”

“Frex! Frex!” Japanese club kids shout, swinging blond dreadlocks. Headphones on, Flex is presiding over the two turntables and a microphone in Tunnel’s elevated, clubhouse-style D.J. booth. The D.J.’s cushy body -- in a red BIG DAWG sweatshirt advertising his newly formed entertainment company -- is wiggling, his long, slender fingers rubbing at the vinyl, then jabbing at the cross-fader, back and forth. All night he flies from his machines to his four strongboxes -- which hold old-school rap, new-school rap, R&B, and reggae, respectively -- flipping through tight stacks of dog-eared record jackets (800 of them), the look and feel of which seem to spark his next idea for what to play. “I never plan what I’m going to play,” Flex says. “It depends on what the room’s like, the ratio of guys to girls -- if there’s more guys, I won’t play a lot of reggae ‘cause that means the girls won’t dance. . . . “

Tonight, as on every Sunday, the D.J. booth is jammed with girls -- all wanting to be seen chilling next to the plump Funkmaster, all looking very Mary J. Blige in their tight Lycra and their Gucci shades. (One, when asked her age, declines to answer. “You might be the police,” she says with a little smile.) But Flex has no time now for the ladies -- he’s got to get this party going. “There’s a point in the night” -- 1:30 a.m., he says -- “where the crowd has to get off, they have to, ‘cause if they don’t get off -- it’s just like climaxing -- it’s not good, it’s not good.”

Flex’s foreplay is the tease. Abruptly, he stops the music -- a Busta Rhymes single he’s been playing (“Where my dawgs at?” goes the refrain) -- and starts doing what purists complain he does just too damn much: talk. “Why can’t he just play the music, man?” one dripping dancer groans. Flex grabs the mike. “I don’t hear enough noise,” he needles the 3,000-strong crowd in his buzzing, baby voice (Flex’s voice is the anti-Wolfman Jack, high in the nose; “Yee-ah,” he says). “This ma’fucker is the hottest thing you’re gonna get tonight. Who’s gonna make some noise? Where my Jersey ladies at?” Flex demands.

His “Jersey ladies” cheer. Flex giggles; he giggles a lot. In his hard, red rubber-soled shoes and oversize trousers, he’s a mixture of hip-hop king and hip-hop clown, always looking for a chance to make people laugh. Even when he comes up short, he’s still playing the songs he knows -- and he always knows -- they want to hear. “I know what makes a kid move,” he says matter-of-factly, “what he wants to listen to, when he’s driving on the highway, when he’s out in a club. . . .”

”Where my dawgs at?” Flex teases the crowd with another riff -- and then halts it again. “I don’t see enough bouncing,” he chides. “It’s already 1:30, and we ain’t even got shit bouncing yet. Where my Long Island niggas at? Where’s all the ma’fuckers making money in here?” “Ooh, ooh, ooh, ooh,” chants the crowd. Flex giggles; they’re playing along. “Ah-ight!” he says with a laugh.

He blasts another few bars -- ”Where my dawgs at?” -- and then he stops it -- again. “This record ain’t for no pretty niggas,” he continues maddeningly. “This ain’t for Cristal niggas -- “

“Ooh, ooh, ooh, ooh -- “ Fists pump in the air. “Where my Harlem niggas at?” says Flex. A lot of noise. “Word the fuck up!” Flex giggles. “Now where’s Queens at?” “Ooh, ooh, ooh -- !” “Ah-ight . . .”

”Where my dawgs at?” Flex gives the crowd the song again; they commence bouncing. Looking around, you think they’ll remember dancing to Funkmaster Flex at Tunnel the way people remember jitterbugging to Tommy Dorsey at Roseland. Flex almost has his climax now. The dance floor’s writhing like a mass orgy waiting to happen, thousands of bodies undulating in the pink-lit smoke.

But again he stops the music, cold. The crowd grows furious -- “Ahhhh!” ”Ah-ight,” says Flex calmly. “I think I know whose house this is.” He pauses, everyone waiting breathless for the answer, which they already seem to suspect. ”Brooklyn!” Flex screams. “Make some motherfuckin’ noise!”

An explosion of throaty calls. Flex throws the song back up -- ”Where my dawgs at?” -- and the boys are smashing into each other, embracing roughly; the girls are rocking high up on their shoulders, fists churning in the air. . . .

Flex played at my Butterflyalbum-release party,” says girl-about-town/international diva Mariah Carey silkily. “He’s the ultimate choice for any event.” Over the last year, the Funkmaster has become the D.J. de rigueur for happening soirées around the city: the MTV Music Awards after-party, the NBA All-Star Bash, L. L. Cool J’s birthday party. (He gets a handsome, five-figure sum for an appearance, same each week for his four hours at Tunnel, ten to two.)

His cachet has quickly translated into a mini-empire. Since Dick Clark, there hasn’t been a D.J. who’s so dominated and exploited a music scene. “He’s off the meter,” Puffy says. In addition to his Franchise Records and Big Dawg Films (now producing Hype Williams’s hip-hop-gangster flick Belly), there’s Flex’s party-promotion company (Big Dawg Entertainment) and, of course, his mix tapes and CDs (Funkmaster Flex, 60 Minutes of Funk, Volumes I and II, which went gold, and the upcoming Volume III, The Final Chapter, coming out in June). “You can only name a few people who can do what he does,” says Steve Rifkind, founder and president of Loud Records, Flex’s distributor. “Quincy Jones, Puffy, Rza, Jermaine Dupris . . . ” Rifkind attributes Flex’s ascendancy to “his brain.”

Certainly one of Flex’s smartest moves was mass-marketing his mixes. His use of top artists in hip-hop and R&B as freestylists on the albums (Missy Elliott, Erykah Badu, Jay Z, among scores of others) increases his power both as a performer and as a broker of cool. “He has enormous influence,” says Abbie Kearse, a producer for MTV News. “If you’re a new hip-hop artist, you pretty much have to be played on his show.”

Oh, and the Funkmaster is also hawking for Mountain Dew and Starter sportswear and “talking to people” about getting his own TV talk show -- “It’s close. I think Flex needs to get into television,” Flex says, giggling at his own use of the third person, a semantic tic often seen in superstars.

“Flex is sexy,” purrs supermodel Veronica Webb. “He has that pretty chocolate complexion. And, of course, stardom is sexy.” Webb, better known for things other than rapping, also free-styled on Flex’s Volume II mix tape, declaring -- now famously, or infamously -- “I am premium pussy.” The line came about while “we were riding around in the limo drinking cosmopolitans after Puffy’s rap roast,” she lets on with a naughty laugh.

It’s hard to imagine when Flex has the time to carry on in limousines with supermodels. “She said that?!” he exclaims nervously (after being told Webb said she found him fetching), quickly adding, “She can’t say that!” Flex has a girlfriend, Monica Joseph, a producer at The Maury Povich Show.

Flex -- who often has to ward off complaints from callers to Hot 97 with “I like to talk!” -- can be shy in person and is admittedly old-fashioned (his girlfriend is a childhood friend “from the local skating rink”). He’s never seen without his trademark deck-of-cards-size pendant of Jesus (with the dazzling diamond eyes and diamonds in the crown of thorns). “I went to Catholic school and my parents wouldn’t let me go outside past eight o’clock,” he says. “I was always inside. That’s how I learned to D.J.”

Growing up in a strict, religious Jamaican household in the Bronx, Aston Taylor Jr. conceived of “Funkmaster Flex” while mixing Michael Jackson and Madonna and reggae records alone in his room. He picked up D.J. skills from his father, a video technician who also spun records informally at parties in the neighborhood. “Watching my dad, I never wanted to play music or rhyme,” he says. “I always wanted to be the one that played the records. I thought that was cool.”