The crowd roars as John Lund thrashes his arms in a punk rendition of Green Day's hit song "American Idiot," playing his guitar made of nothing but air.

"I have absolutely no musical talent," says Lund, a 32- year-old sales manager from Boston who's lived in Finland for four years. "This kind of an air-guitar event gives me the opportunity to express myself as a musician, even though I'm a musical talent vacuum."

Some 20 hopefuls from about the same number of countries gather each year in the seaside town of Oulu, 380 miles north of Helsinki, to rock it out in the Air Guitar World Championships. The meet that started in 1996 as a sideline to the Oulu Music Video Festival has grown to overtake its parent event.

"It has nothing to do with actually playing the guitar," says Jaakko Jokipii, executive director of the music-video festival. "The core of playing air guitar is feeling the music."

Contestants can choose between an invisible electric or an acoustic air guitar and have 60 seconds to perform a solo. Real musical instruments and props are forbidden; only a pick is allowed. The winner gets a handmade Flying Finn electric guitar.

"It was a good test to get up in front of many people and have nothing to hide behind," says Zac Monro, a 39-year-old architect from London who won in 2001, the first time he ever played air guitar in public. "I didn't believe I won. I blanked out for 60 seconds, and as I walked off the stage, I could just hear a roar."

The event started in heavy-metal-crazy Finland, a nation of 5.3 million people where bands like Kiss and Metallica sell out concerts in minutes. The genre's popularity was boosted by the rock band Lordi, which in 2006 won the Eurovision Song Contest, the world's most-watched song competition, singing "Hard Rock Hallelujah."

Lund, whose musical career consists of two weeks as a singer in a high-school heavy-metal band, is passionate about music. That fervor was born one night after dinner at the age of 6, when after getting his first-ever CD, he put on a performance for his parents. The show, to Bon Jovi's "Livin' on a Prayer," complete with costume and lights, showed mastery of the invisible instrument, Lund says.

Air-guitar players are judged on their technique, expression and charisma, and their feeling of the music or "airness," according to Jokipii. Moves range from headbanging and intricate finger work on the invisible strings to jumping and smashing the imaginary guitar onstage.

"The thing has a certain amount of depth to it if you don't just treat it as a silly joke," says Monro, the only person to have won the event twice, and who now organizes the national championships in the U.K. "That has been proven as 20 nations now take part."