Why do 20th-century bodies gird themselves in $1,000 period costumes and worry earnestly about galliards? Twice a week, Frank Roberts, a veritable loony for Renaissance dance, meets with an errant court of dancers, known as the Dupont Circle Consortium, and they rehearse earnestly, as if Louis XIV were waiting impatiently for their next show.

"Nobody's touched the canary, so I figured we'd work at that," says Roberts, slipping one of his period music cassettes into a somewhat more contemporary boom box.

Today they are not wearing costumes of yore. The only period gesture is the green cloth cap that Roberts plonks on his balding head before each dance and flourishes with courtly vigor. "I made it," says Roberts. "It's a generalized cap from the late period of Henry VIII to the early period of Queen Elizabeth I."

Roberts takes the hand of dance mistress Laura Nelson and they wait for the tape to begin. They hold hands, they turn and face each other, they exchange shuffles. They switch positions, grasping hands on the way. He takes off the cap and bows.

"I think it's controlled fantasy," says Roberts later, trying to explain the motivation of his dancers. "It's interesting to see how, once how they wear aristocratic costumes, they become aristocrats. I have watched personal transformations. I encourage that. I say, 'Think haughty, you're an aristocrat.' It's a mixture of pageantry and academic curiosity.

"It's an oddball activity," admits Roberts. "But it's for educated oddballs."

Those oddballs include "psychiatrists, astronomers, teachers and lawyers," according to Roberts. "They tend to be professional. We have doctors, tailors, a lot of computer people. We had a couple of physicists, a couple of artists. We've had diplomats of various levels . . . "

"I'd never done Renaissance dance before this group," says Nelson, a waitress at the American Cafe in Tysons Corner and a five-year Consortium member. She joined the group because "medieval history's my hobby . . . We're all hobbyist dancers, the dancers of those times would have done it for the love of it and not be paid for it. We feel it's appropriate for us to be doing this kind of thing."

Roberts, an anthropologist and former management systems consultant, prefers to call the dances "court dances," which include modern interpretations of dances from the 14th through the 17th centuries such as branles, pavanes, allamands, basse dances, measures, cascarda, canary dances, balletti and dances from the ensuing Baroque period. He is the main researcher for the Consortium, and there isn't an instant when you're not aware of that. Rehearsal seems as much history lesson as Terpsichore, and Roberts exudes Renaissance trivia and post-Dark Ages gossip.

Louis XIV "liked to show off his legs," Roberts tells the group. The gathered dancers also learn the penalty for dancing the rather sensual sarabande dance during the days of the Spanish Inquisition was "several hundred lashes and several years in the galleys for men." The first five foot positions of ballet, he says, are from Belgian fencing manuals somewhere in the middle 1600s. The galliard was encouraged for men to show off their machismo and prevent them from getting hurt in fencing tournaments: "In Cologne they lost 90 knights in one day alone."

The audience for the Consortium may not be the court of Versailles, but the group has performed at the Court of St. James at the British embassy, as well as at the White House. They even taught Renaissance dance to Amy Carter for a period. They've danced at the Smithsonian, the Kennedy Center, the Cloisters in New York and the Dallas Museum of Fine Arts. They had a brief Friday-night stint at Cagney's, normally a slam dancing ground for young new-wavers. They were obliged to discontinue that. "There has to be ambiance," says Roberts. "They had a Bruce Springsteen look-alike contest while we were there."

According to Roberts, Renaissance dance buffs are multiplying in North America. It all started "with a group of key scholars about 10 to 15 years ago and a second generation of scholars has developed from that. Workshops are held in Ipswich, Mass.; Oberlin, Ohio. They've gone out and become court companies, with satellite companies," says Roberts. The main locations for Renaissance dance, he says, are Boston, New York, Philadelphia, Chicago, Minneapolis, San Francisco, Los Angeles and Seattle, as well as the Oregon Shakespeare Festival. There are also locations in Vancouver and Toronto. "We've heard about a group in Chile."

Roberts started by teaching himself to play the recorder, the shawm and shakuhachi (a Japanese bamboo flute) and playing Renaissance music around town with other musicians. It wasn't long before the group decided, after researching that period, to wear appropriate costumes and, later, to add dancers to the roster. The Dupont Circle Consortium was established in 1974 and now has a membership (alumni included) of some 60 musicians and dancers. The group uses about eight dancers and five musicians a performance.

Earlier this year the Consortium participated in the first international colloquium on Renaissance dance in Ghent, Belgium. The event, complete with period sets, costumes and horn fanfares, featured dancers, choreographers and scholars from companies in the Netherlands, Belgium, France, Italy, Germany and England. It marked the first occasion, says Roberts, for Renaissance aficionados from various revisionist parts of the globe to meet and compare notes.

"There was no controversy. Everyone was scared of each other, no one knew how much everyone else knew. We were all very polite, instead of attacking each other . . . The Italians didn't have much of an advantage over us -- they were as mystified over some of the Italian dances as we were."

If anything, being from the New World helped, rather than hindered, American Renaissance devotees. "The Europeans have had a continuous practice of folk dances which have continued since the Renaissance," says Roberts. "There's a temptation that, if something gets hazy, they refer to their folk dances from a later period. They're seduced by their own continuity. We Americans have worked from the original sources. In some respects it makes the effort a little purer. We don't have the intervening tradition."

In addition to rehearsing for performances and teaching dance workshops, the Consortium is attempting to bring Renaissance dance to Washington in a big way. Roberts is hoping Washington can be the headquarters for a biennial Renaissance convention with companies coming from all over the world. But, until then, it's time to work on that branle.

The Consortium will perform at the Pavilion stage in the Old Post Office on the Saturday and Sunday of Labor Day weekend at 1 p.m.

"We'll pull 'em up onstage and teach them some circles," says Roberts.