The amateur rock band from Arlington is ready to start, but leader Ingrid H. Morroy delays rehearsal by poking fun at the tardy bass guitar player.

"That's good enough for government work," she deadpans, even though the guitar's thick strings still twang off-pitch.

The group warms up in Morroy's living room with a salsa version of the 1967 pop classic "Happy Together," with Morroy and her twin, Judith, mixing in Spanish and tweaking English lyrics to spice up the Turtles tune.

"Imagine me and you, I do. I think about you day and night, it's only right," the sisters sing in smooth, indistinguishable voices that fill the townhouse on a recent evening. "Felices juntos. Happy together. Kerry and Edwards."

Arlington's new commissioner of revenue rocks.

During the day, Morroy, 53, is the tax assessor for all property in the county except real estate. After work, she picks up her Breedlove guitar and heads to restaurants, senior citizens centers and Democratic political events to sing and strum with the Constituents, her rock band.

Morroy, a Democrat, began performing informally in Northern Virginia years before friends dubbed her the "Musicianer of Revenue," a nickname she earned after winning the election for county commissioner in January.

Over the past few years, Morroy has met most of the Constituents at work in county government or through the Arlington Democratic Party. Her sister, who works for the World Bank, lives in Reston.

Many people describe Morroy's voice as strong, melodious and articulate.

"It's like a margarita with a lot of flavor and tang and a little salt," said Ruth Goldberg, 45, of Odenton, who had organized monthly open-mic nights at Bangkok Blues, a Thai restaurant in Falls Church where Morroy performs.

The six-member band plays mainly rock, bluegrass and folk music. Depending on the audience, it may add a salsa or tumbao beat. Hip-high congas and lap bongos, both played with the fingers and the palms, create a softer percussion line than traditional drum sets parents often banish to the garage.

A mandolin, resembling an eight-stringed violin that is strummed instead of stroked with a horsehair bow, adds vibrato.

"What's fun about Ingrid is that she is utterly fearless on stage," said Nathan Norton, Arlington's deputy treasurer for operations, who has seen her perform over the past four years. "She'll play anything . . . [blending] songs from different cultures and different countries."

Morroy, a native of Suriname, speaks six languages -- English, Spanish, Dutch, German, Surinamese Creole and Sranan Papiamento, a dialect spoken in the Dutch Antilles. With black, white, Chinese and Indonesian ancestors, she says she does not fit into any census category.

Although she is believed to be the first Surinamese American elected official in the United States, she is modest about her achievements.

"I'm just a little person from a little country in South America coming to a little county," she said. "I don't see myself as a success story."

The first-time elected official spent eight years working in Arlington County Treasurer Frank O'Leary's office before she moved next door to become commissioner, a $99,000-a-year post.

In her first six months on the job, Morroy has increased tax revenue by $125,000, an increase of 56 percent from the same time period last year, without hiring additional staff.

"We're much more aggressive. We actually follow up," she said, referring to a longtime program in which her staff identifies Arlington residents with out-of-state license plates and makes them register the car with the Department of Motor Vehicles. They must register after 60 days of residence or the purchase of a new car.

"If they don't, I'm coming after them," she said. "In a nice way."

While growing up in Suriname, Morroy could expect to find a guitar in all of her relatives' homes. She learned to read music on her own and easily plays by ear.

The twins are the youngest of five children in a family full of musicians. Her father played the classical violin in Suriname, and her mother sang in a band in Indonesia.

In Morroy's office, there is an old, yellowing photo of the twins when they were 2 years old and living in Holland. They look grumpy yet cute, with grimaces on their faces and matching dresses.

"We were scared of people," Morroy said. "We weren't used to socializing with people because we had each other."

More than 50 years and countless performances later, both are confident singers and guitarists. Morroy attributes much of her success to the opportunities available to immigrants in this country.

"It's just that I took advantage of opportunities -- educational and careerwise," she said. "America makes the best acoustic guitars, and I even took advantage of that."

The Constituents will next perform at the Arlington County Fair at the Thomas Jefferson Community Center. The show, at 3:30 p.m. Aug. 21, will be the second for Morroy there but the first for the band.

"Everybody just loved her [at last year's event] and wanted her back," said Lester Morgan, who manages entertainment at the annual fair. "She's a big draw."

The Constituents -- Seth Merritt, left, Judith Morroy, Ingrid Morroy and Carlos Contreras -- practice their blend of rock, bluegrass and folk.