Silence is the spur to geniusfor choreographer Lar Lubovitch

Lar Lubovitch challenges an important assumption about the choreographic process. With a few notable exceptions, music is the great spur to the choreographer's imagination; even if one has formulated an idea or theme before finding musical accompaniment, the chosen music will then determine his movement ideas. Music tells the choreographer what to do.

But the most interesting dance that Lubovitch has made so far is done in silence. In this case, it's the absence of music that seems to have freed his mind and given him access to ideas he has not explored before. This new dance, called ''Big Shoulders,'' was recently performed by the Lar Lubovitch Dance Company at New York's City Center and is now on tour with the company.

The dance's title is taken from a poem by Carl Sandburg describing his hometown city, Chicago. According to the program note, the dance is about Chicago's architecture and the way people move in it.

What ''Big Shoulders'' is really about is how dancers relate to one another as if they were pieces of architecture. Projecting their limbs in any number of clever and visually arresting ways, the dancers rely on one another as walls rely on beams. The dance is a continually evolving display of human structures, of some bodies cantilevering into space while others provide the foundation of support.

Humor is the keynote. A woman slides in between the bowed legs of a tall man as if the space between his legs were a doorway leading into an elegant salon. Lubovitch plays wittily with the idea that on the dance stage bodies can relate to each other in various ways. One goof can cause the house to tumble, and sometimes the pieces don't quite fit. But no sooner has one sructure met its end than another one is in the making. ''Big Shoulders'' is quick, light, and, fortunately, not as windy as Chicago, although it has a nice, breezy air.

Lubovitch's other dances tend to be simple-minded. Whether this is due to the music he chooses or the kind of movement vocabulary he favors is like trying to figure out which comes first, the chicken or the egg. The certainty is that there's a complicity of ideas between music and dance.

It's revealing that, in deciding to make a dance to Mozart, Lubovitch should choose one of his youthful compositions, the ''Adagio and Rondo for Glass Harmonica.'' Because it's by Mozart, the music is charming and graceful as well as youthful. Lubovitch, however, plays into the simplistic side of it by having the dancers move in cliches of courtly gesture and by treating the rondo form as if it were a clever parlor game.

Lubovitch's great passion is for Steve Reich. The mesmerizing yet mindless nature of this music brings forth his most characteristic choreography, an oily sensuousness and streamlined athleticism. There's no doubt of the sympathy between music and dance; in fact, it's the Reich dances ''Marimba'' and ''Cavalcade'' that have won the Lubovitch company its fame and fortune. Those who prefer edge and alertness in their dancing might get drowsy, however. The silence of ''Big Shoulders'' is, ironically, an awakening change.

The Lubovitch company performs at the University of Tuscson in Arizona today; University of Alberta in Edmonton, Canada, March 30, 31, and April 1; the University of California at Irvine, April 3; the Norris Community Center, Palos Verde, Calif., April 4; UCLA, Los Angeles, April 6 and 7; the Goodman Theater, Chicago, April 10-15; and the Harbourfront Performing Arts Center, Toronto, April 17-21.