The Coolidge Auditorium at the Library of Congress is small and plain, but Wednesday night the uncompromised vigor of the Martha Graham Dance Company pushed back the walls and whipped up the air.

For nearly three hours, it felt like the most exciting place on Earth.

It was an extraordinary evening, a tide of exquisite performances of such seminal works by the modern dance matriarch as "Appalachian Spring," "Frontier" and "El Penitente." There was also a world premiere, "An Act of Becoming," which coupled readings of the humorous and telling correspondence between Graham and composer Aaron Copland with muted dancers sketching images from the text. The piece captured the appetite for discovery that characterized Graham herself.

There is but one bit of bad news: There are no tickets left for tonight's free final performance. However, any unclaimed seats will be made available before curtain time; those interested are encouraged to show up early to be placed on a waiting list.

The evening's thrilling climax, appropriately enough, was "Appalachian Spring." The library's Elizabeth Sprague Coolidge Foundation commissioned the crisp, timeless depiction of pioneer American gumption set to Copland's Pulitzer Prize-winning score. It had its world premiere on the Coolidge's cramped stage in 1944.

Immense credit goes to the dancers for tailoring the arc of their step to the space. (Graham clearly had a bigger expanse in mind when she made the ballet. Indeed, on a larger stage it soars.) Especially adept was Tadej Brdnik as the Husbandman, who managed to keep from kicking anyone even as he was bounding exuberantly with thigh-slapping hoedown jumps and spiraling leaps. As his Bride, Miki Orihara injected a birdlike restlessness into her solos, the perfect contrast to Martin Lofsnes' aloof rigidity as the Revivalist and Katherine Crockett's serene, rock-steady Pioneering Woman.

The early works that opened the program read like a road map to "Appalachian Spring's" enduring achievement. In the highly stylized "Heretic," from 1929, a woman in white (the tiny but commanding Terese Capucilli) struggles for acceptance by an unyielding battalion of women in black. Graham, who originally danced the leading role herself, assumed the mantle of embattled but persevering heroine even at the dawn of her lengthy career.

Other solos likewise showed various facets of feminine power, whether in the twisted grip of agony, as in "Deep Song" (wrenchingly danced by Christine Dakin), or in the unrelenting tease of "Satyric Festival Song" (with Fang-Yi Sheu by turns taut and supple), or in the resolute spunk of "Frontier" (danced with palpable joy by Elizabeth Auclair).

"El Penitente," a theatrical work with firmly etched characters and a plot, was more suited to the small stage, using only three dancers and minimal props (created with eloquent simplicity by Isamu Noguchi, who also designed "Spring" and "Frontier"). Brdnik was the passionate, self-flagellating Penitent; the malleable Capucilli performed the three-part role of Virgin, Mary Magdalen and Mother. Lofsnes danced the grim Christ Figure.

Since Graham's death in 1991, her company has been searching for ways to keep her legacy alive beyond safeguarding her choreography. The impulse to show Graham's contribution in a new light led to "An Act of Becoming," developed by company director Ron Protas and Janet Eilber, who will be taking his place. Though in need of editing, the result was charming and revealing, bolstered by the impeccable timing and delivery of actors Tana Hicken, a veteran of Arena Stage, and Jerry Whiddon, director of the Round House Theatre.

"An Act of Becoming" was a refreshing look at Graham and Copland's collaboration, fleshing out the legend and suggesting the careful thought and playfulness that these two perfectly matched artists put into their partnership. Graham wrote of feeling Copland's melodic line in her pulse even before she had ever heard his music. When she finally received the score for "Appalachian Spring," she declared it was "so knit and of a completeness . . . that it takes you in very strong hands." Needless to say, so does her choreography and the dancing of her remarkable company.

The musicians assembled under the baton of the company's music director, Aaron Sherber, provided sensitive readings of the Copland and other scores. The program was presented as part of the Library of Congress's efforts to document and preserve Graham's works, an endeavor that springs from its acquisition of her archives in 1998 and fueled by a recent Doris Duke Foundation grant. May such vital work long continue.

CAPTION: The Martha Graham Dance Company in "Appalachian Spring" at the Library of Congress, where the dance had its premiere half a century ago.

CAPTION: Exquisite agony: Christine Dakin in Martha Graham's wrenching solo "Deep Song."