(FORTUNE Small Business) – When the New York Knicks begin their season this month, Jesse Itzler's performances will have basketball fans jumping out of their seats. But Itzler, 36, isn't the team's newest power forward. Rather, he's the writer and rapper of "Go New York Go," the raucous rally anthem that plays at the beginning of each game to pump up the audience.

Four years ago Itzler co-founded Marquis Jet Partners, a New York City--based company that leases private jets in 25-hour increments. But before he was an entrepreneur, he was an aspiring rap artist. In 1991 he signed a record deal and released his self-described "frat-rap" album, Thirty Footer in Your Face, under the name Jesse Jaymes. The album got play on MTV and cracked the Billboard Hot 100 before Itzler's music career stalled. He kept writing music, though, and in 1993 he was approached to write a radio jingle for a clothing company whose owner happened to be the wife of the Knicks' general manager.

Like any good businessman (and basketball fan), Itzler spotted an opportunity and asked whether he could write a song for the Knicks. "There was nothing like it at the time," he says. He got the go-ahead, and wrote and rapped a short, upbeat rally song. (Sample lyric: "When I say 'New York,' you say 'Go!' " "New York!" "Go!" "New York!" "Go!") It scored big with Knicks fans and got local radio play, and other NBA teams asked him to write rally songs for them as well.

Since then, Itzler has become something of a ghostwriter for the NBA. He has written and recorded rally songs for the Los Angeles Lakers, the Washington Wizards, and the WNBA's New York Liberty, among others. He even wrote "I Love This Game," the slogan and theme song for the NBA itself. An added thrill is the ability to work with his music idols: P. Diddy, Run DMC, and Q-Tip have all participated on updated recordings of "Go New York Go."

Because of the demands of his day job, Itzler must limit his NBA gigs. "I don't have time to do 15 teams," he says, "so I just do teams I enjoy watching." He'll also write songs for teams with players on the Marquis client roster, "because then there's a connection." This season he is updating his rally songs for the Knicks, Wizards, and Milwaukee Bucks.

Itzler was paid just $5,000 for "Go New York Go"—and he still had to hire his own musicians and backup singers—but as his reputation grew, so did his rate. Today teams pay as much as $50,000 for his lyrical stylings. (Itzler doesn't get royalties, however—the teams own their songs outright.)

Aside from the money, one of the perks of being the unofficial rapper of the NBA is that arena announcers occasionally recognize him at games. That happened in Dallas a few years ago. "They put me up on the videoscreen and introduced me as the writer of 'I'm a Mav Fan,' " Itzler says. "I took a bow."

Still, the native New Yorker remains a Knicks fan. "There's nothing like going to the Garden and hearing your song on the loudspeaker with 20,000 people waving their towels," he says. "It's as close to being Jay-Z as I'll ever be."