AVANTE-GARDE. A hackneyed phrase but appropriate enough as a description of the Trisha Brown Company and its riveting three dance performances at the Loeb last week.

Brown begins the first dance--a solo called "Accumulation"--with a simple gesture; turning her forearm over and back at a steady pace, she flips her thumb from side to side. Her other forearm then mirrors the action. She repeats both gestures and adds a third, then starts over again and adds a fourth. After 15 or so "Accumulated" movements, the dance ends. Like the first gesture, the hitchhiker's thumbs wagged side to side rather than held steady as we are accustomed to seeing it. Many of the movements appear out of place but there is a deadpan humor that runs through this dance and the others, a humor which contributes to the uniqueness of the performance.

During the performance, Brown tells funny stories about creating the dance. She speaks in a monotone; she never cracks a smile. The sound of her voice meshes with the pace of the movement, a soothing rhythm of changes. Dry humor is the source of both words and actions.

The effect is a sixties-ish one. Like a pop artist, Brown transforms the banal events of everyday life into art. The art becomes the process of the making of art. Like a minimalist, Brown uses simple, repeatable units placed end to end to build the whole, and by doing so, finds herself playing formal games on stage.

Yet one senses that the conceptual framework is not the point at all.

I went with a friend who loves classical ballet. Reading the program note for the second dance "Locus"--"The score for 'Locus' is a random ordering of 27 points on a cube of space immediately surrounding the standing figure"--she moaned, "It sounds awfully theoretical." But an awareness of the theoretical nuances of avant-garde dance is an initiation to familiarity with the academic language of classical ballet. The initiation makes you an insider, one party to a compact between artist and viewer. Once you're familiar with the compact, you can appreciate the dance as dance.

Dance logic is the way a dance makes sense and communicates its reason for being. When you sense the logic--and with the logic the connection between you and the artist--the grace of the movement is enough. When you don't see the logic you note: it's beautiful but lacks expression, or it's theory but lacks vitality.

Despite the program note describing its formal structure, the formal order of "Locus" is not what matters. What matters is the larger motion--the easy motion of the dance. The spontaneity set within a precise structure and the fluidity of the improvised play with movement much like ballet, only ballet seems to have its logic built into its technique, whereas the logic in Brown's work, and in modern dance generally, comes solely from the choreographer's decisions. Brown's dance--like all great dance--touches the same deep chord: a sense of ease, freedom, spontancity, openness.

THE FINAL PIECE is called "Line Up." The dance premiered last spring in New York and is Brown's magnum opus, incorporating many of her earlier works. Included are four pieces originally titled "Structured Pieces I-IV (1973-1976)," "Sticks," "Mistitled (5 Minute Clacker)," "Spanish Dance," and "Figure 8." "Line Up" includes new material arrived at through "memorized improvisation."

What holds the diverse sections together, in part, is the way the dancers perform. Visually the movement has a quality of matter-of-fact ease. Technically, this means movements are linked without transitions, or that, in Brown's words, "the preparation comes from the momentum of the preceding move." Some consider this convention of performance style among the avant-garde dehumanizing. On the contrary, it seems that performers often impose on themselves an impersonal constraint so that personal statement oozes through the pores of the discipline.

In "Spanish Dance," the only passage of the dance set to music--Bob Dylan's "Early Mornin' Rain"--the dancers perform a predictable yet hilarious task. They begin lined up along the downstage edge of the stage. The dancer furthest to the right swivels her hips and raises her arms overhead, imitating a Spanish dancer. She proudly shuffles her way forward, bumping the next dancer into motion. The two continue to pick up the third and so on. As the music stops, the five pose as a compressed wedge of Spanish soul. What is interesting is seeing the different persona each dancer projects in executing the same action: Elizabeth Garren first, splaying her arms with a measured deadpan delivery; then Wendy Perron, pouting over her twisted hands as she raises them overhead, leaving them crunched over her phooey expression; Trisha Brown next, hunching up her shoulders as if a little too innocent and awkward for such sensual display; and then small Mona Sulzman, sweeping her arms to the side then high, pulling herself up to the height of the others; lastly, Lisa Kraus, like a ship's figurehead with strongly-arched back and triumphant gaze.

Watching the entire performance one senses the significant changes--and utterly different qualities of motion--making its different sections. The sections from "Locus," "Solo Olos," and the set improvisation are concerned mostly with the dancers' place, the moving from place to place, and the movements when the dancer loses sense of place and careens off-center.

A very different dimension opens in "Scallops" and "Figure 8," two sections added late to the piece. In both, the lights dim, and suddenly the dancers inhabit a remote world, a mythic world. Their place is no longer the kinesphere, the space within reach of the human figure. Their gestures relate to the entire space of the stage; the dancers have become larger-than-life.

In the ending "Figure 8," the five stand in a line down the middle of the stage from front to back. To the beat of a muffled-sounding gong, they bring their hands to a spot on their heads, then pull them away, wavering their arms to either side of their bodies. It's the most powerful sort of choreographic imagining. It makes the viewer close eyes and burrow into their seats afterwards, not wanting to let it go, keeping the deathbeat sounding in their minds.