House music rises from massive speakers and fills the dark, crowded club with its pulsing, trance-like beat. Beams of colored light wash across the throngs on the dance floor, tinting the dancers' ecstatic, sweaty bodies blue, red, green. A strobe light distorts their fluid movements so that they resemble characters in a cartoon flip book.

The swirling, sliding music—at once spacey and soulful—spreads out across the crowd like a sonic picnic blanket. The music crescendos and the dancers lose themselves in the expanding beats. They flow in perfect synch with every warp and twist in the track.

Overseeing all of this music and movement, controlling it like the great and mighty Oz, is not a jet-set superstar DJ from London or Ibiza with an ego the size of his MP3 collection. Increasingly, it's a mild-mannered software developer who's in the DJ booth, manning two turntables and a MacBook.

[To learn more about the developer DJs interviewed for this story and the equipment they use, see the slide show, Two Turntables and a MacBook: Geeks Get Their Groove On.]

Laptop- or digital DJ'ing, as the practice of playing and mixing MP3s using a computer and special software is known, has emerged over the last decade, as music went digital and laptops shrunk in cost and grew in power. The use of technology in DJ'ing attracted young men with geeky tendencies—the guys who were members of their high schools' HAM radio and AV clubs, who played in the school band, and who tinkered with robots and electronic devices in their spare time. A decade later, these dudes are still tinkering, only now as software developers and hardware engineers by day and as professional or bedroom DJs by night. They see both traditional turntable and laptop DJ'ing as a way to channel their technical skills toward a creative pursuit that's universally regarded as cool.

"I talk to a lot of DJs, and when I ask what they do during the day, it's some kind of technical job," says Nicholas Maddix, 33, a club DJ and the creator of Anagram software.

Alan Cannistraro, 31, a software developer who works for a computer manufacturer in Silicon Valley, says he was dumbfounded by the number of IT professionals in the San Francisco-bay area who claimed to be DJs when he moved there from Toronto.

"The Bay-area is dominated by people in technology, and the number of DJs here is ridiculously high," he says. "We sit in front of computers all day. We love it, but we all need creative outlets. DJing is a geekier creative outlet."