As Ja Rule spits out the rhymes to "Clap Back," two teenagers -- a white dude with an elaborately carved Mohawk and his beauty-pageant-pretty black partner -- throw down South-Central style in the aggressive form of hip-hop choreography known as "krumping." Another couple does the cha-cha to Los Amigos Invisibales' "Cuchi Cuchi." A third pair stagger like clockwork toys to the emo-rock sound of "Dance, Dance" by Fall Out Boy.

So you think you're watching BET? Telemundo? MTV 2? Think again. This is Fox's "So You Think You Can Dance," a prime-time network talent contest that is proving that unfamiliar music and obscure dance steps aren't necessarily a television turn-off. The two-hour July 19 broadcast of "So You Think You Can Dance" topped four other star-search series -- ABC's "The One," CBS' "Rock Star: Supernova," NBC's "America's Got Talent" and UPN's "America's Next Top Model" -- winning the 18-to-49 demographic that is most prized by advertisers.

The show debuted last summer after the surprising success of ABC's ballroom pro-am matchup "Dancing With the Stars." "So You Think" found its niche by emphasizing a young, culturally diverse group of contestants and embracing dozens of genres choreographed by experts in their disciplines. The show averages between 9 million and 10 million viewers per episode, up almost 20 percent from last year, making it a regular Top 10 program this summer. The season ends Aug. 16 with viewers deciding who will be America's favorite dancer.

The show also can be viewed as a successful marker in social evolution. In "Hairspray," the film and Broadway show now being made into a movie musical, racial integration on an "American Bandstand"-style TV dance show was a big taboo. "Dance is the G-rated version of having sex," said "Hairspray" director Adam Shankman. "And it's not always G-rated."

In 2001, the film "Save the Last Dance" featured a love affair between a white ballerina and a black hip-hopper and raised a few eyebrows. On "Dancing With the Stars" and "So You Think You Can Dance," it's not even an issue. Generating sexual heat between performers of various ethnicities in flashy numbers that treat modern dance and contemporary hip-hop as equally legitimate, the show helps to erase divisive racial and cultural lines.

"It definitely ruffles some people's feathers, seeing an African-American guy dancing sensually with a white girl," said choreographer Anne O'Meara. "But no matter what your beliefs, when two people dance well together, people realize it is an art form and you can't help but sit back and smile."

For Denise Piane, a featured dancer, the show provides a "forum for issues that people aren't necessarily comfortable with, like race, gender and sexual preference."

"It's a dancer's soap opera," said Los Angeles contestant Donyelle Jones, 26, after a recent show.

"You have sex, you have jokes, you have drama, crying, pain," added 18-year-old Aliso Viejo resident and Top 10 finalist Ivan Koumaev.

America is also struggling with a steep learning curve of dance terminology and technique. In addition to recognizable salsa, disco, Broadway and music video choreography, "So You Think You Can Dance" presents the abstract movements of contemporary, the romantic grace of 1920s fox trots, the acrobatics of mid-century swing and the street swagger of today's hip-hop.

"You can't really teach that much on television. We're here to entertain as much of the family as is humanly possible, from grandmas to grandkids," executive producer Nigel Lythgoe said. "The mandate is to challenge the dancers."

Brian Friedman, a contemporary choreographer and frequent guest-judge on the program, says the show is educating the public "not just about the many varieties of dance, but the fact that it is an athletic sport you really have to train for." It is an equal-opportunity field, says Cicely Bradley of the hip-hop choreography duo Nu Stylz, one in which race, height, weight and beauty are largely irrelevant.

Lythgoe makes no bones about how the dancers are paired. "We chose them by their personalities and strengths and what they can learn from each other. It would be too easy to put white couples and black couples together, and whichever way you go, someone is going to say something, so I don't even think about race."

"To do what they do, I would have an ulcer," said ballroom judge Mary Murphy. "Thank God, they're young and don't know any better, because they really go for it, 100 percent."

Much of the show's success, of course, can be attributed to genetics. "So You Think You Can Dance" is the offspring of the ratings juggernaut "American Idol" and shares many of the familiar features of the singing competition created by Simon Fuller, the British talent manager who put the Spice Girls together, and Lythgoe, a boy-wonder choreographer for the BBC in the swinging '60s. In addition to the usual cringe-worthy search and audition footage, the show presents dancers as a highly emotional lot, given to crying, collapsing, vomiting and smiling gamely while being strapped to gurneys.

"Dance," however, is far more in tune with the realities of its industry. "Idols" win lucrative recording contracts; the winner of "Dance" gets a year in the chorus of Celine Dion's Las Vegas show. "Idol" props up the careers of music's eminences grise -- Barry Manilow, Rod Stewart, Queen -- and lets the contestants choose their own songs. On "Dance," the guest performers on results shows are of-the-moment members of the dance-music community, from Euro chanteuse Natasha Bedingfield to hip-hop smoothie Ne-Yo, while the choreographers select the tunes for the dancers.

As a result, the show features reliable oldies, including Irene Cara's "Flashdance ... What a Feeling" and Bryan Adams' "Have You Ever Really Loved a Woman?" as well as contemporary hits by Black Eyed Peas but just as often mixes in "She's Freaky" from the Miami rapper Pitbull, a Liza Minnelli rendition of "Bye Bye Blackbird" and Soundmaster T's "2 Much Booty (In Da Pants)."

"We're bringing these artists to a more Middle-American audience," said Friedman, "and, hopefully, broadening people's taste in music."