Employers: Clubs, promoters, and individuals.

Openings: Promote skills on MySpace or a personal website, then get a booking agent.

Salary Cap: High seven figures for celebrity D.J.'s

Number of Jobs: About 100,000

"The song is instantly recognizable and enchanting," says the 28-year-old Lewitinn. "It's also very haphazard in its own delightful way, being one of the few songs [where the] bridge is the most eagerly anticipated part of the song." Lewitinn says she often chooses to follow up the song with other surefire crowd-pleasers like Prince's "Let's Go Crazy" or Michael Jackson's "Billie Jean."

Though her own tastes run more toward alternative and indie bands like the Oolahs and Bright Light Fever, that doesn't stop her from appreciating many other genres of music and playing what she thinks a given crowd will respond to.

"When you D.J., you understand the concept of a song structure and you get a sixth sense of what crowds will react to and what the masses will react to," Lewitinn says. "All you have to do is close your eyes and think, Can I picture a hundred people singing along to this song?"

Her gigs today range from the party she throws every Thursday night at a downtown Manhattan dive bar to the recent engagement party for power couple Serena Torrey and Teddy Roosevelt V at the Natural History Museum, where Motown and Arcade Fire were the favorites. She also does plenty of weddings in the Hamptons and Cape Cod, which bring in anywhere from $2,000 to $4,000 per gig plus travel expenses; her hourly rate is roughly $250 an hour.  

Lewitinn usually has about 50 CDs on hand with a mix of songs, from George Michael's "Freedom" to Bon Jovi's "Living On a Prayer," when she does parties, tending to play more popular Top 40 songs in clubs while saving the cutting-edge stuff for smaller venues. Unlike many other D.J.'s, she eschews the popular computer program Serato Scratch Live to manage her playlists and instead uses CD players connected to a mixer because of the greater discipline it forces upon her.

Lewitinn started D.J.'ing because she loved music, but she also used it as an excuse to stay out late, since her conservative Jewish-Egyptian parents would only allow her to do it if it was helping her career. After seven years of D.J.'ing, she finally got an agent to deal with payment problems, where promoters often shortchange even popular D.J.'s.

"Promoters sometimes promise one thing and deliver another," says Lewitinn. A bad night at the bar for a promoter, with people not buying enough drinks, means a smaller chunk of change at the end of the night for the D.J., who usually has to wait until 4 a.m. to collect his or her share.

In addition to D.J.'ing, Lewitinn has also become well-known for her tastemaking blog, Ultragrrrl.com—the source of her D.J. moniker. The site gets thousands of pageviews a day from people checking in to find out what she's listening to now.

Despite a brief foray into producing, she says she's now content to play other people's music at parties and help to popularize bands she likes, claiming that the ingredients of a hit song are often a mystery to her. "I'd be much richer if I knew!" she says.