Made for “barely seven figures,” Rigopulos says, Guitar Hero and its sequel, Guitar Hero II, sold more than 2.5 million copies, brought in more than $200 million in combined revenues, and gobbled up the major industry awards. Fans from Wall Street to Warsaw stage Guitar Hero tournaments and “Guitar-B-Cue” parties. The two games are must-have tour accessories for real rock bands. Detroit Tigers pitcher Joel Zumaya sat out the American League Championships nursing a wrist injury—from playing too much Guitar Hero. Viacom took notice of the games’ success and paid $175 million last year to buy Harmonix, making it the cornerstone of MTV’s videogame strategy. “It’s an obvious fit for MTV,” says Van Toffler, president of MTV Networks Music Group. “This is our music gaming play.”

The arrival of Rock Band, which will be sold and distributed by Electronic Arts, is reason enough for gamers to get twitchy. While Guitar Hero was a solo gig, Rock Band enables up to four people to play together, in person or online.

But to Harmonix, Rock Band is much more than a game. It’s a new platform for delivering music and building community online. “We’re not taking on Google,” Rigopulos quips. “MySpace and iTunes are enough for now.

Rigopulos and his Harmonix co-founder, chief technical officer Eran Egozy, 35, are unlikely videogame moguls. The two met while working in the music division of M.I.T.’s renowned Media Lab. They also played together in the school’s Balinese gamelan orchestra. One of their projects engineered a way for classical musicians to augment their performances with computer-generated accompaniment. “[Many projects in the lab] were focused on expert musicians,” Rigopulos recalls. “What was interesting to us was everyone else—the other 99 percent of the population.”

So they made a gizmo that lets users manipulate musical sounds by twisting a couple of joysticks. In spite of its terrible name, Joystick Music, it became the hit of the department. Fellow students and visiting luminaries, including musician Peter Gabriel, lined up to have a go. Rigopulos turned to Egozy and said, “I want to start a company. What do you think?”

After founding Harmonix, in 1996, they released its first product—a consumer PC version of Joystick Music—with high hopes and an earnest tagline: “There’s a musician trapped inside everyone.” It tanked. During a trip to Japan, where music games like karaoke are a national pastime, the two realized they were in the wrong business. Instead of writing music software, they should be creating videogames. There was just one problem: Music games just wouldn’t stick in the United States. The team’s first couple of PlayStation releases garnered critical acclaim but few sales. Even a karaoke title failed to turn a profit.

When RedOctane, a fledgling manufacturer of videogame dance pads in Sunnyvale, California, approached them to create a music game with a guitar-shaped controller, they balked at the high price point and inventory risk. “No reasoned analysis would lead you to believe it would be successful,” Rigopulos says. But that was precisely what would make Guitar Hero a runaway success. Like the music it celebrated, it was an improbable hit, from the tiny whammy bar on the plastic guitar to the gleefully cheesy covers of ZZ Top and Megadeth.

Songs were carefully chosen for their “playability,” says Ted Lange, associate producer at RedOctane. “They need changes in verse and chorus and at least one good solo.” When master recordings were unavailable, a session band covered the songs for the game. Marcus Henderson, Guitar Hero’s real-life guitarist, re-creates the tracks with utmost respect. “I’m a method performer,” he says. “I get my ass in gear and do the research.” He recorded Nirvana’s “Heart-Shaped Box,” for example, with Kurt Cobain’s preferred equipment: a Fender Mustang guitar and a Boss DS1 distortion pedal.