DANCE IS AN ART built on tensions. From the primary element of the working muscle to the elegant patterns of body and space, movement and music, the energy flows back and forth in an interplay of contrasts, daring mind and sense to seize the balance and rejoice in it.

A variety of dynamic tensions characterized all three of the works that the Boston Ballet presented last week at the Music Hall, in the opening series of performances of the 1977-78 season. The program, which ran through Sunday, began with Act II of Swan Lake, the famous moonlit encounter of a prince with the enchanted Swan-Queen. Separating this act from the full ballet proved to be something of a mutilation; it cancelled the careful dramatic architecture of the whole, forcing the audience to view the ballet as "pure dance." Yet this limited view is not totally stifling, as the dance, a supreme masterpiece of the Russian tradition, contains some of the most exquisitely harmonious choreography ever devised--and some of the most demanding. It is structured something like a concerto, the Swan Queen's solos (or pas-dedeux with the Prince) alternating with ensemble passages for the corps de ballet of swan-maidens.

In contrast to solo dancing, ensemble work requires each individual dancer to be as unobtrusive as possible, presenting the onlooker with the paradox of human forms assuming a fluid, abstracted aesthetic function. Thursday's swan maidens were polished, nestling together like the coils of a spring, swirling and clustering in their white skirts like blown dandelion seeds. On the other hand, Laura Young's Swan Queen was, for all her technical competence, thoroughly disappointing. The role is a showcase of breathtaking choreography, but Young moved from pose to pose as though composing the isolated frames of a film strip. A sense of fluid, organic wholeness was entirely lacking, and her uninspired dramatic portrayal had the same quality of something artificially imposed. Young's rather heavy build and stiff upper body contributed to the plodding effect; despite a certain mellow grace, this Swan Queen was far too earthbound.

THE RECENT SOLO WORK Lazarus, which followed the unexceptional Swan Lake, was nothing less than awesome. From the moment Tony Catanzaro's Lazarus emerged from the yellow light of the tomb, crouched like some deformed insect, the struggle of form against space and life against death riveted the audience. Catanzaro used his considerable physical power to convey an intense emotional compression, and as the dance toiled upward from the ground he grappled with space as though the very air around him were thick with death.

The final work was Lorenzo Monreal's version of Carmina Burana. A series of sketches accompanied by Carl Orff's lusty medieval songs, the work is a luxuriant celebration of the pleasures of the flesh. Accordingly, every element in this production was pushed to abnormally heightened intensity. With the placement of the accompanying Harvard-Radcliffe choruses along the walls of the theater, the sound engulfed the audience from all sides, rather than just from the orchestra pit. And the visual scene was intensified by the moving colored lights and the looming shadows of the dancers projected onto a backdrop. And the choreography even stretched the body lines out of frame; a prevailing mode of movement used shoulders and elbows in a fluid geometry of angles and wedges thrust into shace.

The ballet did have some rough edges. For one thing, it was simply too long--the Dionysian assault upon the senses that is the work's major strength cannot possibly be sustained at full intensity throughout all 27 sequences; some of the texts could be eliminated without doing violence to the whole. And not only did the movement often bear a purely arbitrary relation to the music, but also it was internally inconsistent. There were occasional bland passages of traditional ballet figures, as well as moments of apparently random borrowing from other styles, such as Indian dance. Finally, the Harvard-Radcliffe choral groups, singing under crowded conditions, too often suffered from blurred pitch, particularly among the sopranos.

Yet at its best moments, Carmina Burana was a work of splendor and integrity. In the final scene, which mirrors the first, the figure of Fortune is lifted above an encircling crowd: the conical form consummating the angular choreography of the work's most arresting dances--the cyclical theme exulting in the deepest pattern of all bodily life. If the overriding contrast in the Boston Ballet's performance were between a great classic's ethereality and a modern work's affirmation of the senses, there could be no doubt where the Company's own preferences lay.