A HUGE mirror covered one wall of the room. A few chairs were scattered around. Two tables were cluttered with empty wine bottles plastic fruit, masks, and a rubber chicken. Several large black rubber mats lay on the floor -- where the 12 bodies were stretched out.

On a frail-looking wooden chair, a boy sat watching them in silence. He wore blue jeans, a blue shirt, a brown vest, and glasses. His shaggy brown hair curled around his ears. The door to the room squeaked open just wide enough for the head of a girl to stick in. From beyond the door came some giggles, and then the distinct Cambridge twang of a high school student floated into the room, "Look, they're playing dead."

None of the bodies moved. Paul Cooper, the boy sitting down, got up and walked silently over to the door. "Please leave," he said, "We're having a rehearsal." The door closed; and then from outside it could be heard a loud wave of giggles. One of the boys lying on the floor moved slightly. "Jesus," he said. He started to laugh, and the rest of the people on the floor joined in.

WHAT the girlieboppers had wandered into was a rehearsal of The Bonds of Interest, a play that opens tonight on the mainstage of the Loeb Drama Center. Its cast was not playing dead, however; what it was doing--lying motionless, stretched out on the floor of the dance studio--was putting into practice some ideas about acting and drama that are currently taking hold in a lot of Harvard minds.

Formally, under Cooper's direction, the cast was "warming up." At each rehearsal the warm-up takes a different shape; each time, different members of the cast (and sometimes Cooper) lead them. Warm-ups begin with a lot of jumping up and down, a lot of shouting, and a lot of grunting. Slowly, and not surrpisingly, the actors get tired. And with their systems exhausted by jumping shouting and granting, they lie down. That much is very easy -- it's a way of ridding yourself of a lot of minor annoyances that build up in your mind and your body during the course of a day.

Once they are on the floor, however, a different process begins: it is known as "finding your center." "Just relax and find your center," Cooper would say over and over. For most people, the center -- quite literally the center -- lies just below the abdomen, in the direction of the sex. If you're lying on your back, tired out and relaxed, it doesn't take too long to find.

"WHEN you are there," Cooper would say, "your entire self should be there. Let everything you are be right there at the center." After a few minutes, "If you are at your center, and you want to make a noise, please make one." Grunts and hisses and groans, from all the centers of all the bodies, And when the noises stopped, Cooper would say, "Now slowly begin to think about your role. Let your role gradually descent into, your center." A few minutes later, the actors would begin their regular rehearsal.

That people exercise and warm up before a rehearsal does not seem very odd. Athletes do it all the time. But implicit in the kinds of exercises Cooper's cast has been doing is a concept of acting very different from what has often been common in the past. Perhaps it can best be called "gut" acting.

"Take a script of a play," Cooper said one night. "You can approach it in a lot of ways. The most common approach is to try to analyze and understand it. Just who is this character you are trying to play--that's the problem your mind has to deal with. If you understand your character, then you can try to feel like it, figuring out for yourself the whole pattern of its stage life."

To the extent that an actor succeeds in feeling like his stage role, he will be convincing on stage. What Cooper has tried to do with his cast in The Bonds of Interest is to get them into character not only through the mind--but through the "center" as well. If an actor can find his center and then make his stage role part of that center, uniting the literary creation with his own gut, he can actually become the character he is trying to create. For the few hours of the play, the transformation will be real. Acting will, as one of the members, of Cooper's cast explained, be "a total thing, instead of an intellectual game."

THAT IS THE first goal of the warm-ups. The second is to build up energy among the cast. "This play," Cooper told his actors at a rehearsal last week, "isn't going to make it on literary merit. It isn't going to make in on plot line. If it makes it, it will be because we're sustaining it on our own energy."

He said that after a particularly bad run-through of the second act--one that was dead, joyless, dull. Cooper then said, as his cast sat on the floor around him, "Now I want you to get up and walk around." They did. A minute or so later, he said, "Now start to make noises at each other. Make a noise and make it at someone." What happened was very eerie to watch; for the actors began to grunt at each other, and then, as though high on the action around them to physically contact each other, bumping, then shoving, and in one case, actually fighting. Suddenly, big waves of energy were flooding the room where minutes before there had been none.

After about a minute of this, two of the actresses, playing a noblewoman and her beautiful servant, moved away from the rest of the people toward the corner of the room from which they come on stage to open the second act. As they moved, they talked to each other, half as their characters, half as themselves, improvising their lines. Then, as they stood arguing, Cooper said, "All right, come on. Come on." And, as the rest of the cast was silent, the two girls cut from their improvised dialogue to the lines which open the second act. This time, as they came on stage, there was a tremendous amount of energy flowing back and forth between them.

THE WARM-UPS, exercises, games, and improvisations that Cooper has used are by no means new to the stage. His play, The Bonds of Interest, is an imitation of Comedia dell' Arte--which grew popular in Italy and France in the 16th century, and later saw such variations as Punch and Judy shows. The original comedia were performed by troupes of players --who traveled from town to town with their entertainment. Their plays were never the same, however. What were constant were the roles that each member of the troupe played and a few basic plots and themes: true love thwarted by a preposterous and often evil father, cunning servants who devise ingenious tricks and ruses, the soldier and the harlequin, etc. Each night, before the performance, the leader of the troupe would give his actors the plot twists for that night--with a few variations on character and theme, a few new disguises. From there, the characters worked out gags of their won, and once on stage it was their won creative, improvising ability that made the plays a success.

Five or six weeks ago, when Cooper began work on The Bonds of Interest, he wanted to try something similar. He took the play, and wrote a synopsis of the action--a plot and character outline, which he then presented the actors: no stage directions, no cues, no lines--just a glimpse of the plot, and the characters who are in it. From these bare guidelines, he hoped the whole production could grow.

NEEDLESS TO SAY, it was an ambitious undertaking; and Cooper soon abandoned it. "It was simply too much to ask of a group of actors, some of them with little experience, working together for the first time." So the cast fell back upon working with scripts. But Cooper left many of the scenes unblocked, trusting the actors' onstage imagination to do the work for them. "Because a lot of the play is unblocked," Cooper says, "and because we've worked a lot with improvisation, the play will be a little different each night. But that's fun."

It also raises some problems. Although the actors enjoy the liberty that Cooper gives them, it puts them in an awkward position. For if they manage to get as fully into character as Cooper wants them to, to get their guts into the play, and if they are able to build up a high enough energy level to sustain the play (as they have in rehearsals early this week), they remain uncomfortably burdened with the play itself. Their onstage exuberance has at times been so great that it has totally swamped the action of the plot.

This prospect does not worry Cooper as much as it might some other directors. For one thing, as he admits, the plot of The Bonds of Interest could be swamped with little loss to anyone. (It is about two companions who arrive at a town. One assumes the role of a nobleman, the other his crafty servant, and so on.) For another, he is not terribly worried about putting on a technically polished production of the play. "After all," he explains, "we are a group of amateurs. There's something a little pretentious about our trying to present a very elegant, very polished production of a play. What's much more important, at least for this play, is that we all have fun with what we're doing. As in the original comedia--that's a lot of what the play is about. And if we can have fun with it, the boisterousness will carry over to the audience."

THOSE, at least, are Cooper's hopes. But much of what he is doing is new to him. He began as a techie, then took Hum 105 last spring, and directed Ruddigore this fall. He has a closely-knit, energetic cast; but Cooper will admit that he often doesn't know where the energy will lead.

He is also burdened with a play that was by no means his first choice (although its author, Jacinto Benavente, won the Nobel Prize for Drama and the original production of the play ran for more than 850 performances in 1907). A week ago, Cooper's own energy level was so low that he didn't even know if he would really want to put on the play.

But things change rapidly in the world of the theatre. And "with no pretensions about theatrical perfection," he is once again excited about the show. "In some ways, the play makes a lot of sense to me," he said a couple of days ago. "It is a comedy of masks and masquerades. Mostly people talk with their masks up, but sometimes the masks are down. Maybe that is the way the world is."

Cooper would scrupulously deny that he sees an intellectual message in the play, however. He has given it a generous amount of spectacle, as well as some modern touches. And for the past week, the frenzy has been slowly mounting--as opening night grows closer, as more and more scenes have to be reworked (on Sunday, Cooper and two of his actors rewrote the entire first scene), as the costumes, lighting, music, and set all have to be pieced together with the acting.

Saturday night, the cast finally moved up from the dance studio on to the mainstage. "It was like being a naked drowning body," one of the girls said, "to be suddenly confronted with so much space, so much emptiness, with nowhere to turn for reassurance." Since then, they have grown accustomed to the stage. But they won't know how much reassurance they can count on until the audience sees it tonight