In a garden room hung with exotic puppets, Joan Singer sits on a chrome-and-cottom chair, hooks a bare foot around the chair leg and leans boldly into a haunting violin melody.

The room swells with the sound of Gabriel Faure's "Pavanne," as played by Singer and her three companions -- Martha Delaney (second violin), Libby Blatt (cello) and Jan Albright (viola).

Somewhere in the second section, the music breaks into discord. Speaking in a kind of musical shorthand, the women discuss tempos and downbeats, note and specific measures where things went wrong.

As suddenly as the music stopped, it starts again in scrupulously maintained harmony.

The women are the Cameron String Quartet, a for-hire foursome that has been in the music business three years.

Started "because Martha had a friend who needed a quartet for her wedding," Singer recalls, the group took to the streets of Alexandria "one glorious October day" in 1977, and moved inside the Torpedo Factory "when it got too cold."

"We played there forever," Delaney remembers with a groan, "but it was a great experience -- a good audience."

Blatt says the Torpedo Factory work helped the quartet discipline itself, add to its musical repertoire and brought some though not much, money.

"It bought gas for all of us in those days," Delaney said.

But the quartet hit a professional turning point just two years ago at a music workshop at Rutgers University. At the workshop, sponsored by the American String Teachers Association, the four women met string quartets coach Jorge Gardos.

"(He) told us we had something really special going," Delaney said.

"And, made us promise to get together four times each month," added Singer.

So far, even though finding rehearsal time in their conflicting schedules is often difficult, the quartet has not disappointed Gardos.

Their busy schedules, say all four women, reflect their many interests. Everything from skiing (Albright -- U.S. Ski Patrol) to vegetarian cooking (Singer -- teaches in Fairfax), from piano repair (Blatt -- "oldest apprentice in the Piano Technicians Guild") to business administration (Delaney -- enrolled in the master's program at George Washington University), from acting (Blatt -- amateur) to puppets (Albright -- Puppetelle Productions), from mothering (all of them) to other musical groups (Bach Consory, various jazz groups, Fairfax Symphony and a school program called Hello, Symphony).

"We're four very different people" Albright says, "and we each bring something unique to the group."

The differences strengthen the quartet, they agree, even though there are occasional tensions.

"Making the quartet work is as hard as keeping a marriage together," Singer says.

"Twice as hard," Blatt chimes in, "because there are twice as many people, and you have to bend . . more than you want."

"And be tactful" Delaney emphasizes, "and don't dominate. It can be a horrible situation if one person tries to dominate."

The group treasures this independent tone. "Four people listening to each other," as Albright puts it. "The quartet is a good way to perfect our playing and musical sensitivity, since we're constantly matching someone else."

This unconducted blending adds a certain spontaneity to their performaces. Singer comments: "The most we can do in rehearsal is set the stage. The performance is a creative process -- something organic, almost."

But the quartet looks to the first violinist -- Singer -- as its natural leader, and she handles the business end of the music group.

"I have to find out all the dirty details about a job," she says. "If they need costumes -- we have 18th century costumes -- or stands, or chairs, or lights or whatever, we're prepared."

The quartet tends toward classical concerts -- "We do Gadsby's Tavern in our costumes," Singer says -- but plays a variety of styles from Strauss waltzes to show tunes, from Scott Joplin to "something funky like Mac Davis," from backround music to original works by Kent Hart, an arranger in Vermont who occasionally sends made-for-quartet works.

Hart also "discovered" a Mozart piece the group played at a concert on the composer's birthday.

"We told (the audience) this piece was recently unearthed -- a fact they accepted without blinking -- and then started in playing 'Happy Birthday' in the Mozart manner," Singer: said.

"After a bit, I started to hear all these little tee-hees rising from the audience. Then they turned into real guffaws, and finally the whole place was roaring. It was great!"

The group enjoys "almost all" its jobs and has roamed as far as West Virginia to do them.They open businesses, help raise money for politicians, tune up for weddings or "do intimate dinners for two -- we'll even sit in the other room," Blatt suggests.

At a recent interview, the group readied itself for such a romantic evening, discussing the tone the Faure piece should take.

"It describes four women walking through the forest, where they meet up with some men and have an argument," Albright explains. "We're trying to decide if the argument should be a real squabble, or something a little softer."

Tenderness wins out over turmoil, as the quartet decides to mute the cello and turn the war of the sexes into a mild lovers' spat. With that Singer's foot curls around her chair leg once more, and the Cameron Strings sing.