Mary Fitzgerald is often mistaken for an angel. So are Dotian Carter, Carolyn Gregg, Susan Saurwein and Rhonda Smith. Not one of them sports a halo or as yet has sprouted wings. But they do play the harp.

People "expect you to be an angel. But you have to work like the devil to play like an angel," says Fitzgerald, the Navy harpist who, with a flutist, provides the "downstairs entertainment" for guests arriving at White House state dinners like the one tonight for Canada.

And audiences "expect you to be dripping in chiffon, with long hair flowing down your back," says Carter, the National Symphony Orchestra's harpist, adding that even among musicians, the harpist is perceived as the "beautiful one in the orchestra, and stupid on top of it."

Are harpists dumb, frail creatures who just play pretty music? Absolutely not. They are serious musicians who have spent years training.

Before the finger tips start plucking, all the strings on the concert harp have to be tuned. It's a tedious process that can take up to half an hour (there are 46 strings on some harps, 47 on others), and it often must be repeated several times during a practice session or performance.

Harpists have to develop strong upper arm, back and hand muscles in order to place their hands in the unnatural and, at first, uncomfortable postions that good harp form demands. They also have to coordinate moving the seven pedals that change keys. And like violinists, guitarists and cellists, harpists experience some pain until they develop calluses on their finger tips.

"We're not shrinking violets," says Smith, who plays in the Air Force band. "It takes a lot of strength and a lot of guts, because chances are you are the only harpist in the orchestra or band. When the conductor points at you, there's nobody there to help you."

"It's hard to be dainty, delicate and fragile when you have to heave the 60-80 pound instrument around," says Fitzgerald.

In the grande dame era, when the harp was played as a parlor instrument by wealthy ladies, harpists almost never carried their instruments. Now harp training includes instruction on how to carry it.

Many players prefer to carry their harps themselves because they're worried that people unfamiliar with handling the instrument will damage it. "I once had a harp totaled," says Carter. "They dropped it and split a large piece of wood. It was like someone had taken an ax to it." With harps costing between $15,000 and $20,000, it's a risk harpists can't afford to take.

Still, audiences are somewhat taken aback when the "angel" of the orchestra walks off with the harp.

Carter recalls that once, after she performed at the Library of Congress, two "huge guys" came out to help her get the harp offstage. When they asked her what they should do, she told one to take the stand, one to take the bench. She took the harp.

"The whole audience broke up. I didn't even think about it. It just is natural for me," she says.

Eventually the harp does wear out, and getting the money to buy a new one is not always easy. One harpist ended up getting a home improvement loan -- bankers apparently don't react well to making harp loans, particularly if the musician doesn't have a contract with an orchestra.

And finding a job is no picnic either. Most orchestras use only one full-time principal harpist, preferring to hire a free-lancer when a piece of music requires two harpists. Orchestra positions don't open up all that frequently -- Carter has been with the NSO for 17 years, Fitzgerald with the Navy for eight -- and when they do, the competition is fierce.

*Like other struggling musicians, harpists play in restaurants, at private parties and with small orchestras and chamber groups. Saurwein, for example, plays with several local orchestras and entertains the brunch crowd at the Grand Hotel on Sundays.

"Most people are real polite," she says about restaurant playing. "They ask a lot of questions but they also have a lot of misconceptions. I mean people ask for 'On the Road Again.' I could probably play it, but Willie Nelson does it a whole lot better. It's just not appropriate on the harp."

Gregg, who plays as Carter's second in the NSO, has her share of party and restaurant war stories. "Some people are nice and some act as though you are going to vacuum the rug or something," she says.

Once, when she played on a hospital ward, one of the patients was convinced he had landed in Heaven, she says.

"I was playing Christmas carols and was really into the music. After a few minutes, I realized a lot of people were running into one room. I thought they were going to get coffee but somebody's heart had stopped. The doctor told me later that when the man was revived and woke up, he just kept saying, 'I'm in Heaven, I'm in Heaven.'