Two chairs, four stools and six dancers face a mirror-lined wall in the studio where choreographer Stuart Sebastian sits, straightbacked and in command.

Near his side, Arlington Dance Theatre's new artistic director Carmen Mathe watches and works the tape recorded music.

Sebastian, 27, and the dancers are at work - listening, talking, walking, joking, humming, dancing together. This mix-up is all part of day-long sessions in which Sebastian is "setting a new work on the company," in the language of dance.

The piece they are rehearsing is the world premiere of "Moving Right Along," created by Sebastian for the six-member ADT company.

"It's my first attempt at jazz," the New York choreographer explained."The music (by contemporary composer Claude Bolling) is very classical jazz . . . for piano and flute. I want to show we can be jazzy and still have classical ballet."

The work is also geared to America's television-oriented viewers, he said.

"We're working with an audience raised on TV. This work is fast-paced, because that is what the public has gotten used to in films and television. It has to be fragmented and move right along, as the ballet title says," Sebastian said.

"'Moving Right Along' is a light, fun ballet. Very dancey," ADT's Mathe added. "It's based on classical techniques but much freer. Even the costumes suit the mood of the music, sort of based on dancers' practice clothes: tights, leg-warmers, head scarves, T-shirts over leotards . . . They're artfully designed to look the way dancers look when they rehearse, very colorful and gay," Mathe said.

The new ADT company's opening concerts, tomorrow, Saturday and Sunday, will give Northern Virginians a world preview of Sebastian's latest work. The free-lance choreographer has also composed dance pieces for the Metropolitan Opera, the Joffrey II Company and The Royal Winnipeg Ballet, among others.

Arlington Dance Theatre's resident professional company is unusual in the metropolitan area because its dancers are fully salaried for a 44-week season. Mathe was named artistic director earlier this year and immediately started a pre-season search for new members of the company.

The new director is a former prima ballerina with the National Ballet of Washington. She joined that company in 1971 and remained until it disbanded in 1974. This year, Mathe added to ADT another former National Ballet member, Fred Martin of Fairfax. He joins two other ex-National dancers, Andrea Price and Libby Wade, who along with Ken Ludden were already members of ADT when Mathe became its director. The remaining two dancers in the company of six, Della Weinheimer and Stephanie Godino, were recruited from New York.

"Since my medium is classical ballet, the company's concentration will be on that," Mathe points out. Her emphasis is also on getting talented guest choreographers, most of whom are friends and colleagues, to create new works for the dancers, she added.

Along with Sebastian's ballet closing the December program, a work called "Songs" by choreographer Bryner Mehl will have its premiere performance. "Songs" will feature the entire company dancing to four songs by Strauss, with piano and baritone.

New works for programs planned later this year include "another modern piece by Virginia Freeman (a Washington choreographer) in April and something by Ben Stevenson of Houston in January," both contemporary works based on classical techniques, Mathe said.

In ADT's future, Mathe sees a real need to expand the company. "For six dancers, carrying a classical ballet load is a terrible burden. If one dancer is off . . . " she says, leaving the sentence unfinished. "We must get another male dancer next year."

"Hopefully, we can also get together with the Arlington Symphony. I feel very strongly about having affiliation with them. We have to be separate groups, but need to work together. ADT wouldn't have to use taped music then," she added. "Also, if we're doing long-term planning, we'd like to have our own home, our own theatre. If they want to have a professional company, that's how it must go.

Mathe pointed out that ADT offers, through the performing arts office of the recreation division, a variety of classes, primarily in classical ballet, with some jazz, tap and modern, at many levels of instruction for all ages.