LET ME BORROW from Clive Barnes: AIR is beautiful. In her program notes, Lindsay Ann Course writes, "Mixed media has yet to be legitimized. Once that is accomplished. I believe we will discover that this polygamy of motion, sound, and light is the basic art of the theatre." After seeing AIR, I believe her; for the parts of her program fit together so well that you are not aware of the mixing. The dance, the music, and the lighting are not three art forms but one-which men, out of their fondness for such things, have tried to tear apart, isolate, and destroy. Miss Crouse has given us the gift of putting them wonderfully back together.

AIR is structured in four movements, each movement built around one of the classical elements--water, earth, fire, and air. But the elemental imagery is not strict. Like everything else in the program, the images flow into one another, joining and drawing strength from each other.

The second movement--earth--is probably the most exciting. It opens with movies of Cambridge projected on the white backdrop. First is a film of Hilles Library, speeded up many, many times so that the people in it tear up and down the stairs with greater energy and bustle than the Keystone cops at their peak. This sequence gives way to one filmed outside Memorial Hall, also speeded up many times. The dancers than come on stage, their movements exaggerated and fast. The music continues loud and rapid, and the audience is suddenly caught up in this frenzied, hell-bent, crash-course ritual we all know so well. Some call it Cambridge; Miss Crouse calls it earth.

A SLIDE sequence follows. The dancers grow angrier, more passionate. The music begins to sound like the fire of machine gun bullets, interspersed with air raid sirens. The slides and music literally assault your senses, but they assault the dancers as well; at the end of the movement, when the dancers stretch their agonized hands high in the air, their shadows projected 20 feet high on the screen behind them, they are not groping only for themselves, but for all of us.

One of the joys of AIR is that it exists in the senses and the emotions. It does not have a message or need a message, because it is its own message. Peter Ivers' music fits the program brilliantly, and the lighting--by Alessandro Vitellie, Ken Chang, and Richard Strother--is nothing less than fantastic. There are times--as in the second movement when a violent, fiery red light floods the stage, then yields suddenly to a gaunt, blue, empty light--when the light seems like an ether in which the dancers exists, so closely a part of their dance, that they are indistinguishable from it.

The dancers themselves--the Dance Theatre Company of Cambridge--are uniformly excellent. Either you mention none, or you mention them all. I will mention them all: besides Miss Crouse, they are Rika Burnham, Deborah Chadsey, Edith Hathaway, Nadine Hurst, D. Scott Kemper, Wakeen Ray, Ginny Roe, and Peter Stevens. Besides being very good, they are all very beautiful and seem to have a consistently good sense of what they are doing. At times, they are so relaxed that they virtually play with their movements, drawing them out and enjoying them like a poem.

THE PROGRAM is short, ending around ten, and the fourth movement--air--is less than ten minutes long. But it is the show's highlight. A cross-stage projection of red and blue light allows the two dancers--Miss Crouse and Miss Hurst--to use the depth of the stage in an extraordinary way. They move their faces and bodies in and out of the light, being and not being. This movement's score consists of music from the other three movements, recorded in an echo chamber, wailing back and forth across the stage like the turning of the spheres of the universe.

There is, however, a fifth movement to AIR. Miss Crouse did not choreograph it, but it fits so well into the program that she would be proud of it. If you go to AIR, watch for this movement: it comes during the intermission, right after Cambridge-earth, and is about ten minutes long. The lights go up, the applause trails off people rise from their seats, move around, look nervously other people, scratch their heads, light cigarettes, and start to talk. To talk and talk and talk. To move and look and scratch and light and talk so fast that they should be in the movie sequence of Hilles. IT was at this point that Miss Crouse's art suddenly became out-rageously vivid, but last night nobody seemed to realize it.