It would be hard to conceive of a program better calculated to reveal what the Dance Theatre of Harlem is all about, or to show its dancers off to more gratifying advantage, than the one the company introduced at the Kennedy Center Opera House last night.

"Square Dance," which the troupe added to its repertory this year, is a modern neoclassical work by George Balanchine, who was DTH-founder Arthur Mitchell's mentor, and the source of much of the company's early repertoire. "Banda" was staged for DTH last season by its creator, Geoffrey Holder, whose fusion of African, Caribbean, modern and classical idioms is uniquely suited to the versatile capacities of the Harlem dancers.

David Lichine's "Graduation Ball," another new DTH acquisition for 1983, demonstrates yet a third, contrasting facet of the troupe's activities--the cultivation of 20th century classics in a multitude of styles, this one from the Ballet Russe de Monte Carlo treasury.

"Square Dance" is vintage Balanchine, fast, brilliant, and fiendishly difficult, and its conception--exploring, as John Martin once put it, "the common roots of folk dancing and the academic ballet"--is ingenious. DTH has been criticized in some quarters for mixing elements of the original production of 1957 (the on-stage "caller") with Balanchine's revision dating from 1976 (with the orchestra in the pit, rather than on stage, and an interpolated male adagio).

It's hard to see what's wrong, however, with the company assimilating the work to its own image and audience, especially when no violence is done to the integrity of the choreography, and when the dancers perform it as rousingly, cleanly and stylishly as they did last night. As the lead couple, Judy Tyrus and Eddie Shellman had a crisp Balanchinian clarity; the women managed the tricky gargouillades (fancy jump steps with trilling feet) splendidly, and Shellman found an apt gravity for the extraordinary adagio solo.

"Banda" wasn't created for DTH, but it's hard to imagine another troupe getting quite so spellbinding a hold on it. It's a voodoo danse macabre, a theatrically electrifying pageant of death and mourning according to Haitian tradition. Holder designed it from top to bottom, including the hauntingly evocative backdrop, the stunningly coordinated costumes, the musical score--utilizing Gregorian and native chant, percussion and solo flute--and the startling choreography, compounding African, classical and contemporary idioms into an amazingly forceful unity. Lowell Smith as the Man with Coffin, Karen Brown as the Mother, and the entire ensemble of mourners and priests were excellent; Donald Williams' portrayal of the voodoo lord, Baron Samedi--part satyr, clown and specter--was genuinely thrilling.

"Graduation Ball," that frothily nostalgic period comedy about Viennese cadets and girls on the eve of graduation, was staged for DTH by Terry Orr of American Ballet Theatre, and the new production establishes a viable midpoint between gentle burlesque and affectionate sincerity. Neither Donald Williams nor Lorraine Graves and Karen Brown could muster quite the pyrotechnical voltage for their virtuosic variations last night, but Tyrus, Shellman, Yvonne Hall and Karlya Shelton danced outstandingly.

Last night's program will alternate through Sunday with Tuesday's admirable opening bill, featuring "Les Biches," "Pas de Dix," and "Firebird."