Harmonix has even bigger plans for Rock Band: to make it the destination of choice for online music downloads, including songs for MP3 players, videos, and gameplay.

“You can imagine that you can purchase a playable song, and with another click, you can own [the MP3 version of] the song,” Toffler says. Harmonix plans to introduce new artists as well, just as MTV did for years in music videos. “Bands already want to release songs in Rock Band,” says Rigopulos. “It becomes like new radio for major bands, indie and unsigned.”

Of course, once players start downloading songs and creating their own bands, the natural thing to do is find a way to bring them together. That’s where MySpace-style social networking comes in. Rock Band creates a forum where players around the world can create profiles, interact, and swap music recommendations.

But there are potential stumbling blocks. “I personally think it’s being ambitious beyond its ability with Rock Band,” says Michael Pachter, an analyst with Wedbush Morgan Securities. Harmonix is unproven as a developer of peripherals; it needs to not only make workable instruments but keep up with production demand. Across the internet, gamers are grumbling, hoping there won’t be a prohibitive price point for Rock Band. Harmonix says it’s committed to keeping the price low and suggests that consumers will be able to buy instruments individually. The online component, though, is potentially more daunting. All internet activity is prone to delays, and the slightest hitch could cause players to jam out of sync.

Harmonix may also face competition from its own brand when Activision, which now owns the Guitar Hero franchise, releases Guitar Hero III—currently in development by Neversoft and RedOctane without Harmonix’s participation—this holiday season.

At the end of every day at Harmonix, the gamemakers rise from their desks and take the elevator downstairs for what has become a company ritual: the jam session. A windowless storage room has been converted into a sort of mini CBGB. There’s a black-light poster with neon mushrooms on the wall. There are guitars (real ones) and battered amps, a tattered pirate flag, and a light system hanging from the ceiling. A beat-up drum kit floats in a sea of splintered drumsticks.

Yet despite Harmonix’s rapid expansion throughout the building, a few law and accounting firms remain. The other tenants haven’t taken kindly to the heavy-metal feedback pounding through the walls and have set a restriction, much to Rigopulos’ chagrin. “They told us we can’t play until after six,” he says.

Harmonix won’t be playing by anyone else’s rules for long: It will soon be leaving this building for a larger space in town. There’s no telling how much further it will go when Rock Band mania hits and the players take over. “You can smash as many of our guitars as you want,” Rigopulos says with a smile, “and we’ll happily sell you some new ones.”