The go-to song guru

It takes a village to make a Top 40 hit, and, today, there's a town meeting at the Chalice Studios in West Hollywood. The songwriter in chief is Kara DioGuardi, the project is a British soul singer named Lemar, and the goal is clear: write an American pop hit, from scratch, before the day is out.

This is a typical day for Ms. DioGuardi, the brains behind the blondes, brunettes, and boy bands who populate today's music charts. At 36, writing songs for artists half her age, DioGuardi is the Diane Warren of the US Weekly generation. Most recently, she wrote and coproduced two tracks on Britney Spears's new album, "Blackout" – songs that may well save the flailing starlet's career.

Since she scored her first hit with Kylie Minogue's "Spinning Around" in 2000, DioGuardi has developed a diverse clientele and a staggering portfolio of hits, including Christina Aguilera's "Ain't No Other Man" and Gwen Stefani's "Rich Girl." With over 60 songs on her résumé, she was named 2007's Pop Songwriter of the Year by Broadcast Music Inc., the industry's performing-rights organization.

"I go to Kara with every record I make, and it was no different with Britney," says Teresa LaBarbera-Whites, vice president of A&R for Jive Records, which releases "Blackout" on Tuesday. She's very much about keeping it believable and real for the singer. I knew Kara would be a great creative force around [Britney], and she was."

Today, DioGuardi is figuring out what, exactly, Lemar wants to sing. He brought in one of his own songs, "Mayday," which DioGuardi asks the engineer to blast from the speakers every time a new person stops by the room. "I listen to it in the car over and over," she gushes, "I'm going to try to get it on 'Grey's Anatomy.' "

DioGuardi's enthusiasm for her clients is sincere, and, accordingly, she feels free to tell them when a song doesn't work. Sitting on the floor of the tiny mixing room, legs splayed, playing with her pet chihuahua, she bobs her head as she evaluates some sample tracks Lemar has brought with him. "I don't hear this for you," she says, shaking her head at a synth-heavy, Timbaland-type track. Another song seems promising, but DioGuardi looks puzzled. "These chords aren't resolving properly," she concludes.

Dressed in winter boots, black leggings, and a long, grey sweater, DioGuardi is petite but easily commands the room with her magnetism. Everyone, including the chihuahua, follows her to a studio room across the hall to get to work. She's decided to make a song out of thin air.

"There's a trend going on right now – the street is taking over pop," DioGuardi says in an interview at her Hollywood Hills home earlier in the day. Today's hits, she explains, come from "sitting in a room, having a producer pull up a beat and just vibing it out, in the realest, most in-the-moment way." As an example, she cites Rihanna's hit, "Umbrella," which was produced by Christopher "Tricky" Stewart and Terius "The-Dream" Nash.

"The days of [saying], 'Conceptually, we should write a song called 'Umbrella,' and it'll go like this,' are over. Kids are too hip to that game," she explains. "You'd better be real or you'll get tossed out."

DioGuardi might seem an unlikely candidate for taking the temperature of the "street." Born and raised in Westchester, N.Y., she earned her degree in political science at Duke University before flying to Los Angeles to take a job at Billboard. A singer since age 2, she used her Hollywood network to get her songs into the hands of label executives. Though her own recording deal later fell through, the songs had a life of their own.

"I've known Kara since she was just starting out, and I've watched her come on the scene, take it by storm, and take it over," says Ms. LaBarbera-Whites. "One day she's working on a pop record and one day she's working on an urban record, a country record, a Latin record. A great song transcends all cultural barriers, and she knows that – and she's also capable of writing it."

Though DioGuardi has yet to win a Grammy, she may have her chance with two songs on Céline Dion's new album, due out in November. DioGuardi says it was rewarding to write for a woman her own age, who has the voice to deliver. With teen singers, though, DioGuardi is no less devoted. She is a perfectionist who still agonizes, for example, over a single word in Kelly Clarkson's "Walk Away." The word "attention" in one line should really be "intention," she says, to fit the song's emotional "thesis."

"I'm not a poetic writer at all," DioGuardi adds, unabashedly. "If you wanted me to write a [Bob] Dylan song, that Dylanesque-type song would be the biggest piece of [rubbish]. I'm just trying to express emotions in a way people can understand."

And she must express them in a way that is believable for the artist. "Most people think that the artist that they've fallen in love with has written the song. It doesn't dawn on them that it could be somebody else, and when they find it out, they wish they didn't know," she says, soberly. "This is their fantasy, and that's what music is. It's about escapism."

Having climbed the highest songwriting mountains – rescuing Britney may be the Golden Fleece of the songwriting industry – DioGuardi has lately devoted her energies to developing her publishing company, Arthouse Entertainment, and its roster of 10 young songwriters. She has been holding "writing camps," where a label sponsors the studio time for her team in exchange for a first look at the songs that result.

For Lemar's new song, DioGuardi called in Zukhan Bey, who wrote the ubiquitous hip-hop head-bobber "We Fly High (Ballin')" and Emanuel Kiriakou, who wrote Nick Lachey's comeback single, "What's Left of Me." Lemar tells the team that he wants a song based on a conversation he had the night before in which he encouraged a friend to stick with his girlfriend – despite their fights.

And so it starts: DioGuardi asks Bey to set a "lights-out" mood with the drum machine, and Kiriakou strums through chord progressions on a guitar. DioGuardi hums and babbles, scat-singing a melody into existence before she belts out the chorus: "Stay where you are."

She has the hook, and she repeats it – standing, sitting, jumping, gesturing as if she were on stage herself. Lemar, whose tone has the epic quality of Seal's, joins her on the note and begins improvising lyrics of his own. A pop song is born, in less than two hours.

"Nothing makes me happier than a good song, whether I wrote it or somebody else did," says DioGuardi, as her co-writers look on. "I know how long it takes for that bus to come by, and it's a moment that needs to be celebrated."