Raising a Ruckus : Irish band the Cranberries is a hit that no one quite expected. The fans can’t help singing along.

The crowd begins to sway with the opening strains of the Cranberries’ hit “Linger.” On stage, Dolores O’Riordan sings earnestly through a few bars of this emotional tune, then looks up and smiles.

“Go on,” she tells her fans.

At which point, thousands of voices rise in unison while she simply mouths the words.

“Do you have to . . . do you have to . . . do you have to let it linger.”

This scene, videotaped at a London concert last year, replays itself in arenas and music halls around the world. Fans have made a startling habit of turning the band’s concerts into joyous sing-alongs.

Not that the Cranberries are entirely unaccustomed to warm receptions. Their first two albums produced a string of hits and the critics have generally raved. Still, the notoriously shy group of musicians from Limerick, Ireland, hardly expected such a commotion at their live performances.

“When it first started happening, it really took us by surprise,” said Noel Hogan, the band’s guitarist. “It gets a bit loud sometimes, but it’s far better than a crowd that just sits there and looks at you.”

Los Angeles fans will get their chance to raise a ruckus at a sold-out Universal Amphitheatre tonight. If the Cranberries’ most recent Southern California concert is any measure, the evening could prove noisy.

After that show--at the Wiltern Theatre in November--Steve Hochman, a Times pop music writer, was left to ponder why a performance that he graded as “pretty good” inspired an overwhelming response.

“The roars of devotion that greeted the group seemed appropriate for an act that had been around for decades, the emotion with which fans sang along on almost every song was suited to certified anthems, and the worship that accompanied O’Riordan’s every move should have been reserved for a true force of nature,” Hochman wrote. “C’mon, folks!”

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Similarly, a recent profile in Rolling Stone magazine noted that the band’s “low-key delivery is often subsumed by audience din.” Fans struggle to explain their behavior.

“I do agree with (Hochman) to some extent, but the Cranberries are much deeper than most ‘popular’ bands,” said Eugene Takaaki Shindo, 19, of Berkeley, a veteran of five Cranberries concerts. “Nothing beats the moments you’re up front in the open-seating area, lighting your lighter during the quieter songs like ‘No Need to Argue,’ singing along to ‘Linger’ and dancing to the fast songs.”

Said Joseph Robert Longoria, a 23-year-old San Antonio man who follows the band by way of an Internet fan club: “I cannot explain the reasons I am compelled to clap and sing along. It just happens.”

The Cranberries’ rise has been every bit as unexpected. Their 1993 debut album--”Everybody Else is Doing It, So Why Can’t We?”--quickly pushed its way onto the regular rotation at both alternative radio stations and the more influential MTV. A 1994 follow-up, “No Need to Argue,” produced two hit singles--”Zombie” and “Ode to My Family”--and sold more than 5 million copies.

Hochman attributes such success to a “mix of restless romanticism and sophisticated melodiousness (that) has spanned generations, striking a chord with young alternative fans and more sedate boomers.”

Fans suggest that the Cranberries have continued a musical tradition that began with earlier alternative bands both in Europe and the United States.

“Their soulful lyrics finish what The Smiths started a decade ago,” said Sharon Dang, 22, of San Diego. “And I’m not talking about the whole Generation X Angst movement . . . they have created music that’s not just reaching out to teens but also to adults.”

Yet even staunch followers were less than dazzled by the band’s early live shows. O’Riordan refused to face the audience, standing sideways while she sang. Drummer Fergal Lawler and bassist Mike Hogan were similarly sheepish. Noel Hogan played guitar with his head down.

Crowd response changed all that.

“At first, we weren’t too sure if we were good or bad,” the guitarist said. “But when you see a crowd that’s really into you, you do get a bit more confidence.”

Now the Cranberries are mentioned in the same breath as such Irish luminaries as U2 and Sinead O’Connor. So O’Riordan feels brave enough to encourage singing and chastise quiet audiences. The reluctant quartet from Limerick goes so far as to include a quick Irish jig in each performance.

“When the crowd’s really, really good,” Hogan said, “you go for it a bit more.”