In a dimly lighted church basement room, six young women of widely assorted sizes and shapes mill around, stretch and bend, tug at leg warmers and adjust tape recorders.

Rehearsal is about to begin and the tension of an upcoming major performance is keenly felt in the room. As the melodic chanting of Benjamin Britten's "Ceremony of Carols" begins, the mismatched figures suddenly meld into supple, flowing ribbons in a vibrant, joyous dance called "Celebration."

The title is apt: the six women in their twenties, who comprise Contemporary Dancers of Alexandria (CODA), are rehearsing the opening number for the group's first anniversary performance, which will take place on Saturday at Francis Hammond High School in Alexandria.

CODA, Alexandria's only professional modern dance company, is the fruition of a dream of veteran Alexandria dance teacher Hedi Pope.

Pope -- now an apple-cheeked, vivacious 60 -- retired in 1975 after 32 years of teaching: "I wanted a performing group (then), but I had my family to raise and that would have been more responsibility and time than I could handle."

But after retirement, "things had a strange way of falling into place," Pope said. She enlisted the services of Carol Anderson, a former student whom Pope praises not only for artistic ability but for a "fabulous sense for raising money."

Anderson, 24, who has a bachelor's degree in dance from Florida State University and a solid background of training and performing with such professionals as Twyla Tharp and Jan Van Dyke, now dances with CODA and serves as its studio director.

"Carol also attracts friends," says Pope. One of these, a former college acquaintance named Victoria Hileman, is now CODA's artistic director and principal choreographer.

In 1978, Anderson, Hileman and four other dancers took $750 from the Performing Arts Association of Alexandria and "geared up," as Pope put it, with local appearances. This was followed last March by a performance of works in progress at Christ Church, CODA's home base in Old Town. Anderson also continued to run Pope's dance classes for children and adults.

With the help of friends in the community, many of them Pope's former students, the group has in the past year incorporated as a nonprofit organization and received the tax-exempt status that permits performances such as the benefit at Hammond.

The group also has received state and federal grant money, and private contributions from local organizations and businesses. It has the devoted services of what one spokeswoman calls an "amazing group of volunteers" who do everything from public relations to cleaning the studio, often in exchange for free dance lessons.

The dancers, too, fill diversified roles, making or improvising their own constumes, choreographing, teaching. Each dancer has at least one job teaching dance either for CODA or some other area group.

Their schedules are, by necessity, unconventional -- "One 9-to-5 person would blow the whole thing," said Pope -- so that they can rehearse together in Alexandria for two hours a day.

CODA has performed locally at the outdoor lunchtime program in Market Square and at the Alexandria Community Y's Christmas Walk, as well as with groups such as the Alexandria Performing Arts Chorale.

It also has performed areawide by invitation for Dance Project, the Modern Dance Council's Dancers' Showcase and the Round House Theatre. CODA is also one of nine companies selected from among 37 that auditioned to appear in a three-day, areawide dance showcase called City Dance 80, May 8 through 10 at the Warner Theater in the District.

The company's appeal lies partly in its versatility. Nearly all the dancers have trained in classical ballet as well as modern technique. Elements of both are obvious in the dances they will perform Saturday.

The graceful leaps and elongated body lines of "Celebration" will be followed in the program by a spritely duet entitled "Country Smiles." Choreographed by Hileman and performed by Carrie Lukeman and Judy Matthews to the music of an electric violin, the dance uses bent elbows, flexed feet and a hoedown tempo to take a humorous look at life on the farm.

Another Hileman creation, "Nightshadows," is "the only dramatic piece now in our repertoire," according to the choroeographer. In an eerie but beguiling composition that stretches the dancers' technical abilities to the limit, they dart about singly and then mass together to the soft all-percussion music of a cantata by Argentine composer Alberto Ginastera.

The common characteristic of CODA members, says Hileman, is that all "are very attuned to their bodies as instruments and adapt well to different styles." And that serves CODA's purpose well. Hileman says she wants "to establish this as a touring repertory company that is versatile -- that can go in and out of different styles."

As if to prove the point, the second half of Saturday's performance will include dances by three different choreographers: "Duet," by CODA dancer Cathy Paine uses the music of a radio station selected at random by the dancers as they come on the stage; Limelight," by Washington choreographer Elly Canterbury, dramatizes dancers trying to upstage each other; and "Six Sections of Orange," an early work of another Washington choreographer Jan Van Dyke, is actually six diverse but related short pieces, each performed by varying numbers of dancers.

So far, the small size of the group does not seem to overtax the energy of any of its members. "We have talked about enlarging the group," says Pope, "but deep down I think the dancers are resisting. They work so well together and have become such good friends."

Also appearing at the performance at 8 p.m. Saturday at Hammond, 4646 Seminary Rd., will be singer LaRene Flack, and CAISO, a calypso steel drum band. A reception will follow the performance at the Ramada Inn, I-95 and Seminary Road. General admission is $5; single tickets for the performance and reception are $10. For further information, call 998-6411 or 684-7573.