After a decade in the karaoke business, lounge owner Kagura Muto has heard her share of sour notes. But business of late has been a different sort of flat.

Under the white-hot spotlights at her bar, a retiree cut loose a raucous, rough-on-the-ears rendition of "I Left My Heart in San Francisco." Nary a soul was there to clap.

"Ten years ago, this place would have been packed with 20 people," Muto complained after punching in the next song for the off-key crooner. "Now nobody wants to sing. It's all because of the bad economy."

Considered by many Japan's most insidious export since Godzilla, karaoke blossomed into a global, multibillion-dollar business after its 1971 inception by a Japanese rock-and-roll drummer who couldn't read a note of music.

Fanatics rave about its "health" benefits, drunken bellowers consider it the great social leveler and the uninitiated find it hard to resist -- at least once. Karaoke has become as universally recognized as Mount Fuji, and sing-along soundtracks provide alter egos for millions of Sinatra wannabes from Laos to Las Vegas.

But in the land of its birth, karaoke buffs are singing the blues.

Japan's decade-long economic slump has spurred a five-year slide in the number of both karaoke bars and singers. Some of the nation's biggest karaoke companies are abandoning the business, while others are trying such innovations as karaoke songs on cell phones and karaoke for the car.

Fans decry the decline of the only pastime that lets tone-deaf crooners indulge their inner Madonnas.

"Karaoke can't die," insisted Yumiko Fujii, who was crowned the country's No. 1 karaoke songster in November at the All-Japan Karaoke Throne Battle. "It's really too bad people are spending less money on it. Karaoke's like a vitamin pill for the heart."

Karaoke's decrescendo began with the collapse of Japan's booming economy. Soaring corporate bankruptcies and record unemployment forced a budget-strapped public to cut back on karaoke nights that often cost hundreds of dollars.

The number of participants peaked in 1994 and has tumbled nearly 20 percent since, according to the "Karaoke White Paper" released in October by the All-Japan Karaoke Industrialist Association. The number of karaoke venues began decreasing two years later and has plunged 16 percent since as more shops go belly up.

Still, that leaves 48 million Japanese behind the microphone -- ample evidence karaoke is far from its final refrain.

Japanese sing karaoke an average of 10 times a year, and thousands enroll in classes. Several karaoke channels are standard fare on cable television. Train stations are still surrounded by multistory, neon-lit karaoke palaces, where Japanese gather in smoky "boxes" with sticky floors to belt out tunes and throw back beers.

But industry officials warn that the downward trend has just begun and is taking an increasingly bigger bite out of the $7.3 billion-a-year business.

Giga Networks Co., a major maker of karaoke machines, was among the first to leave the field. It said selling downloadable ringing tones for mobile phones is more profitable.

Tokyo-based Clarion, the first to mass-market karaoke equipment in the 1970s, followed suit. Its karaoke sales had tumbled 50 percent over the last 10 years.

Karaoke is also a victim of a passe image.

"Nowadays, young people would rather spend their money on their mobile phones," said karaoke's 62-year-old inventor, Daisuke Inoue, who compares karaoke's sliding fortune to the Japanese fads for bowling and billiards that boomed then faded.

Karaoke is trying to freshen its image.

Some karaoke machines now calculate how many calories a singer burns, or they play music-tailored workout videos. Others measure the singers' pitch and tempo, and rate their singing prowess.

Toyota, together with several karaoke firms, has developed karaoke for the car.

Then there's dial-a-song. Just ring up the karaoke hotline on your cell phone and download the latest hits to serenade innocent bystanders. Taito Corp. is working on a karaoke machine that will automatically "fix" a singer's voice to smooth out noxious notes.

For the hard-core crowd, all that is just a diversion from the authentic karaoke. For them, it's more than a hobby; it's a lifestyle.

Yumiko Fujii, left, who was crowned Japan's No. 1 karaoke songster at the All-Japan Karaoke Throne Battle recently, sings with runner-up Nakao Matsunaga in Tokyo.