In the game a player manipulates a toy model of a guitar that uses buttons rather than frets to produce notes, which are color coded on the screen to match the buttons. The music accompanies a rock song with the player simulating the experience of being onstage with the band. The player can move up from an easy level to tougher tests until he reaches the expert level, which takes a high degree of expertise.

That Guitar Hero has appealed to real artists came as a bit of a surprise to the creators. Alex Rigopulos, the chief executive of Harmonix, said he expected it would appeal mainly to “those of us who want to experience what it feels like to play rock music.”

But he said, “We started getting all this fan mail from real artists.”

Partly, the game simply touched the competitive streak in a lot of musicians. Mr. Robertson said he had played against a “really techy geek” in a competition in Denver. “And he beat me.” That night Mr. Robertson invited his opponent to watch a Barenaked Ladies concert and he razzed him from the stage. “I bet you can’t come up here and try it with a real one,” he said.

Artists also simply enjoy the experience of playing someone else’s music. Mr. Robertson said he was so excited to learn the Foo Fighters song “Monkey Wrench” that he went out and bought three of the band’s CDs.

For MTV the expanding popularity of the game is fueling all kinds of ideas for future applications. (One that already has emerged: The Guitar Hero wedding, with a competition at the reception.)

Mr. Toffler said MTV is looking into ways to adapt the game into its television programming. One application that fits nicely is an inclusion of the game in the online “virtual world” MTV is building on shows like “Laguna Beach.”