THEATRICAL activity tends to be heaviest from fall through spring, but summer, in many ways, is a natural time for dance. It's a season for the shedding of clothes, and inhibitions along with them, and hence a logical spur to an art that depends on maximum freedom from physical and psychological constraint. It's not surprising, therefore, that many significant developments in dance have taken place in summertime, especially in this country, where fondness for the outdoors is almost an article of faith.

Summer dance has generally coalesced around those functional potpourris known as "festivals," and among the multitude that have come into being since the early decades of the century the most venerable and still one of the most pretigious is the Jacob's Pillow Dance Festival, cradled in the Berkshire hills of Massachusetts not far from Tanglewood. The Pillow, as devotees affectionately call it, has been going since 1933, when it was founded by one of America's leading dance pioneers, Ted Shawn, who originally established it as a haven for his celebrated troupe of men dancers, whose mission it was to demonstrate that dance art and masculine athleticism were not contradictory concepts. From this beginning it evolved into what Shawn liked to regard as a "university of the dance," in which all aspects of the terpsichorean and sister arts, primitive and advanced, classical and contemporary, domestic and foreign, were taught and practiced side by side.

Washingtonians have a particular reason for interest in the Pillow at the moment, since this summer (two weeks ago, to be exact) the Washington Ballet was added to the long list of companies that have been boosted toward national attention through exposure at this festival. The fact is that such renowned international troupes as the Royal Danish Ballet, the Netherlands Dance Theatre and the National Ballet of Canada, among many others from across the globe, made their first appearances in the United States at the Pillow, and for domestic dancers, a Pillow appearance has long been considered a prime step toward mass recognition.

On the down side, the Washington Ballet performances were saddled with a number of disadvantageous factors. The handsomely rustic, 600-seat Ted Shawn Theatre, built in 1942 and designed by Joseph Franz, the architect of Tanglewood, was the nation's first theater intended exclusively for the use of dance. As such, it has a splendid sense of country intimacy, and a fine dance floor. The stage, however, is very modest in dimension, particularly in height. The ballets by the Washington troupe's gifted resident choreographer Choo San Goh -- "Double Contrasts" and "Fives" made up the Pillow program -- ideally require a broad, high expanse as visual background; Goh's dynamic, space-eating choreography looked uncomfortably compressed in this setting. The company, moreover, was recalled from summer recess for the occasion, and with a minimum of rehearsal seemed not quite tuned up to its own best level of technical security and cohesion. A further detriment was the split programming -- in accord with a Pillow custom, the Washington company shared its performances with Diamond, a small youthful troupe making its formal debut on these programs. Unfortunately for the combination, both troupes favored driving, high energy, up-tempo dancing, and though Diamond's inchoate, superficial material was no match for Goh, the juxtaposition didn't help either company.

Despite all this the Pillow appearance was an important milestone for the Washington Ballet. The company is at a stage of development which makes broader exposure an imperative, whatever the risks -- it must begin to test the waters beyond its local perimeter, and experience the challenge of unfamiliar environments, audiences and critics. The Pillow engagement was, in a way, a preamble to the troupe's approaching debut in the New York area this November, where the stakes will be higher still. In the face of shortcomings, the Pillow performances reconfirmed two fundamental company strengths: the sense of freshness, vitality and commitment emanating from the dancers, which are attributes lacking in many more seasoned troupes, and the durable appeal of Goh's imaginative, brilliantly crafted choreography.

Meanwhile, the Pillow faces challenges of its own. The place reeks of tradition. The three dance studios are housed in barns that were part of the 150-acre estate Shawn purchased in 1930, along with an amiable farmhouse that still serves as festival headquarters. Nearby is the large, bulbous rock outcropping, christened Jacob's Pillow (relating to the biblical tale of Jacob's Ladder, where Shawn's own ashes were scattered. The interior walls of the theater and other buildings are hung with scores of portraits by photographer John Lindquist, who has been capturing celebrated dancers at the Pillow for more than 40 years. The stage echoes to the trend of an incredible parade of dance notables who crossed its boards, ranging from Shawn and Ruth St. Denis to Charles Weidman, Jose Limon, Agnes de Mille, Alicia Markova, Anton Dolin, Antony Tudor, Lucia Chase, Asadata Dafora, Alvin Ailey, Paul Taylor, merce Cunningham and hundreds more, as well as companies and individuals from Scotland, Spain, Samoa, Sweden, Chile, Guatemala, India, Ceylon, GERMANY, england and almost every other place on earth where people dance.

The catholicity of this spectrum is a reflection of Shawn's own hankering for an open-ended, all-embracing community in 1972, the Pillow was run by a succession of people -- Shawn's colleague John Christian, critic Walter Terry, Charles Reinhart (who now heads the nation's "other" festival, the American Dance Festival in Durham, N.C.), choreographer Norman Walker -- who tried to steer a course between fidelity to Shawn's aims and keeping abreast with changing times. This year, an enterprising new artistic director has taken office -- choreographer, director, producer, dancer and educator Liz Thompson -- and she seems determined to hew to a similar path, while at the same time accelerating the "modernization" of the Pillow. Such entries in this year's performance lineup as the avant-grade Trisha Brown Dance Company and the exciting Loremil Machado's Afro- Brazilian Dance Company are indicators of the directions she's heading in. "I really think of it as return to Shawn's original concept of the Pillow, as a showcase for whatever is new and current in dance, within the broadest possible stylistic framework," she says.

Though the Pillow is only in operation during the summer, her job is a full-time, year-round affair. Fund-raising is a good part of it, inevitably. Although the Pillow earns some 80 percent of its $400,000 budget through tuition and ticket sales, Thompson must devote much effort to drumming up the rest from such sources as the National Endowment for the Arts, the Massachusetts Arts Council, private donors and corporations.She's also responsible for planning and supervising the performance series, audience development activities, the school (in which 110 students will spend nine weeks this summer receiving instruction from a faculty of 16), and a burgeoning "outreach" program taking dance into the surrounding western Massachusetts communities. Thompson, like virtually everyone who has some contact with the Pillow, draws inspiration from the site itself. "The place is magic," she says. "Somehow this space holds the collective energy o f all the years past -- it's what gives me my own impetus." Her plans are manifold -- she'd like to involve artists from other media in the Pillow, poets and sculptors, for instances; she wants to integrate the school and the performing artists more fully (this year the student Pillow Dancers will perform works by three of the resident choreographers, including Choo San Goh); she hopes to revive Shawn and St. Denis classics for the Pillow's 50th anniversary in '82; and she intends to undertake more cooperative ventures with other neighboring arts facilities like the Berkshire Theatre Festival (there's a joint project this year) and Tanglewood. Like her predecessors, though, Thompson wants fundamentally to remain true to Ted Shawn's generative vision. "I've inherited a wonderful, lively tradition," she says, "and I see no point in messing with it."