When Mayor Martin O'Malley took office six months ago, most folks thought his days of moonlighting in his own Celtic rock band were numbered.

Think again.

The mayor has used his political celebrity to parlay his band, O'Malley's March, into a much-desired East Coast act. Since being inaugurated mayor in December, the group has delivered its rock-influenced Irish folk tunes and O'Malley originals at such respected music venues as the Kennedy Center in Washington and Meyerhoff Symphony Hall.

Tomorrow night, the five-member Baltimore band will open at Pier Six for big-time rockers Los Lobos and international Irish legends the Chieftains. Last week, officials from the city's annual Artscape festival announced that O'Malley's March will kick off the event on July 21, opening for rhythm and blues diva Patti LaBelle.

Meanwhile, the group's second CD, "Wait For Me," is outselling Grammy-award winning Santana at local Bibelot book and music stores.

"It came out the same day as the N 'Sync CD," said Josh Greenbaum, music supervisor for Bibelot's Canton store. "And it blew it away."

O'Malley has no illusions about the reason for the band's sudden stardom. He knows that the five and six calls per day requesting that his group appear at everything from wine festivals to fund-raisers is spurred by his unique position as mayor of the 16th-largest city in the United States.

The former city councilman handles the new-found band attention with the same self-deprecating humor that endeared him to Baltimore voters.

"The election has finally allowed the band to receive the artistic recognition it has long deserved," O'Malley said, chuckling. "I told them we wouldn't play at Pier Six unless Los Lobos and The Chieftains closed for us."

That comment echoes an exchange from two months ago, when the mayor met new Baltimore Symphony Orchestra conductor Yuri Temirkanov.

I have heard that you are a musician, the renowned conductor told O'Malley.

"I'm not a musician," O'Malley replied. "I'm a performer; the guys I play with are musicians."

Musician or not, O'Malley is gaining national attention with the shtick. NBC's "Today" show taped his recent appearance with the Baltimore Symphony Orchestra. National Public Radio did a 12-minute feature on the singing mayor for its Saturday version of its news program, "All Things Considered."

Rudy: not a rocker Shortly after being elected, O'Malley lamented that he might have to give up his love for playing music due to his round-the-clock duties as mayor and father of three young children. But as his playing schedule dwindled, friends and family noticed that the impatient mayor was much more short-tempered when he wasn't out playing every few weekends.

Just as some people reduce stress by jogging, reading or bowling, O'Malley burns it off rocking with his band into the wee hours. After a recent week negotiating the removal of barrels of hazardous chemicals from a South Baltimore warehouse, O'Malley spent the weekend singing and jumping around the stage of one of his band's regular haunts, Mick O'Shea's Irish Pub and Restaurant on Charles Street.

"I went for a couple of months without playing, and then a weekend came up, and I played both the Friday and Saturday night, and going back to work on Monday, it was as if I'd been off for two weeks," O'Malley said. "My wife's realized that I'm a much happier person if she lets me out to do this every once in awhile. There's something therapeutic."

And those at the shows don't seem to mind the sight of the mayor of a major city, dressed in tight-fitting blue jeans and a black muscle shirt, downing a few pints of Guinness up on stage.

It's not as though O'Malley can leave the mayor's job completely behind while playing, however. At O'Shea's recently, O'Malley got regular reminders, both pleasant and not so pleasant.

During one of the band's breaks, police officers with the mayor's executive protection squad notified him of three non-fatal shootings that had occurred in a two-minute span just after midnight. Moments later, a woman from New York visiting Baltimore approached O'Malley to shake his hand.

"Somebody told me that you're the mayor of Baltimore," the woman said. "Are you the mayor?"

O'Malley rolled his eyes at the visitor, answering: "Yes, I'm the mayor."

"That is so coooooool!" the woman replied. "I could never imagine Rudy Giuliani doing this."

Some slack for the mayor In addition to being good public relations for Baltimore, the act isn't hurting O'Malley politically, the pundits say.

"It's integral to his personality and, this early in his administration, personality is especially important," said Carol Arscott, a political consultant who tracked last year's mayor's race.

Even downtown business types who initially worried that O'Malley's choice of recreation may not appear "mayoral" have come around, the mayor says. CD sales have been so brisk that the band recently hired an accountant to sort out the profits. O'Malley says he will likely give the proceeds to his wife or donate it to charity.

The mayor says he appreciates city residents being tolerant of his side job. And he had better hope that tolerance continues. The band is booked for one weekend a month through the end of the year at O'Shea's, and next month will play the Ram's Head Tavern in Annapolis, a locale that regularly hosts pop music legends.

"I think all of us need to have a passion for some art or reading or poetry or plays beyond whatever our jobs are, because that's what really keeps us here," says O'Malley. "People in Baltimore kind of like it, and they've been very, very kind and decent about giving me my space to do it -- and not getting upset that their mayor is in a bar at 1 a.m. on a Saturday night."