The stage was dark. The curtain, drawn. And the crowd, ready to rock. A hundred lucky fans perched on the edge of their seats waiting for the invitation-only show to begin. Suddenly, the drapes parted as the joyful opening riff of ”I Want to Hold Your Hand” filled the room. The spotlight shone on a drum kit bearing the iconic black-and-white logo of the Beatles.

But the performers twisting and shouting on stage were not four young men from Liverpool. Nor were they members of any of the many Beatles tribute bands. The group performing at the Los Angeles Convention Center this past June consisted of six scruffy young geeks. A long-haired coder belted out the verse. A tattooed woman and a cheery guy added the harmonies. A stocky Asian-American played what appeared to be a tinier version of Paul McCartney’s familiar Hofner bass. Another guy held a likeness of George Harrison’s Gretsch guitar. And a really enthusiastic player smacked the drums.

All were employees of Harmonix Music Systems, a video-game company in Cambridge, Mass., and they weren’t actually playing the song; they were demonstrating the most hotly anticipated new game of the year, The Beatles: Rock Band, which hits stores worldwide this month.