TOKYO -- Every Saturday night at 12:30 a.m. millions of young Japanese tune their televisions to a rock band contest that has changed the face of pop music in Japan.

In only 1 1/2 years, the show "Ikasu Band Tengoku," or "Groovy Band Heaven," has become the hottest late-night TV program. It has introduced more than 650 amateur bands, from middle-aged office workers to rockers with their hair dyed blond.

Several of the bands -- Kabuki Rocks, Norma Jean, Jitterin' Jinn -- have moved from the show to the top of the pop hit charts, displacing the naive and cute teenagers who emerge through the established system of so-called "idol singers."

The program's name is usually abbreviated to "Ika-Ten," which also means fried squid. Last year, the editors of a dictionary of modern Japanese chose Ika-Ten as the most popular new word in the country.

The program has boosted sales of musical instruments and seems to have turned music from something most young people listen to into something they do -- or want to do.

There are at least 20,000 amateur rock bands in Tokyo alone and many more nationwide, estimates Akira Nishikawa, former producer of the show and vice president of Tokyo Broadcasting System, the commercial network that started the show in 1989.

Judges on each show pick a winner from 10 contestants. If the winner repeats for several weeks, the winner gets a chance to make a record for professional release.

But whatever these rockers are saying, it's not the time-honored idea of rebellion and protest.

"We are not playing rock to protest against society or the government. It's been done before, and that's old," says Shinji Wajima, guitarist and vocalist with Ningen-Isu, or Human Seat. "We want to sing about the weakness of an individual, and something about how we can be more human."

Wajima's three-man, hard-rock band launched its professional career in July. Until it appeared on the show last year, Ningen-Isu was unknown.

The amateur band phenomenon owes something to karaoke, or singing along with a tape or video (popular in Japanese drinking places). It also was influenced by the street in central Tokyo that is given over to rock bands every Sunday afternoon. Dozens of groups perform weekly, demonstrating that some Japanese youth exuberantly break out of the straitjacket and stereotype of study and career.

In those street concerts, "performers and audiences are equal, which reassures them that they are not alone," says Tatsuya Iba, a writer for the magazine Let's Start a Band.

The magazine has seen its circulation grow to 300,000, and every month it runs 30 pages of ads from people looking for band members.

Osamu Nakano, communications professor at Hosei University in Tokyo, says Japanese youth do not know what to protest against or what to demand, and the point of the bands is to have fun with friends.

"Playing brand-name guitars in the spotlight, they are trying to experience superstardom," Nakano says. "But they know that it is not for real."

Nonetheless, the band phenomenon has spread to Japan Broadcasting Corp., the public television network. It is organizing a national rock tournament, to which more than 4,100 amateur groups and individuals -- much more than it had expected -- have applied. After regional contests, 20 bands will compete in November's final competition, to be broadcast over the network's satellite channel.

And what are the bands saying? Here's a lyric from a Ningen-Isu song, "Tears of an Apple," sung to heavy-metal guitar crashing by bassist Kenichi Suzuki with violent shaking of his head:

"When a mountain crow cries, a village girl picks an apple. Why, why, thinks the apple, why am I forced to be alone ...?"