Rocking in Rhythm.

That jazz backbeat keeps Billy Siegenfeld flying high

As the song goes, "It don't mean a thing if it ain't got that swing." Early in his career, when asked to describe the sort of music he was making, Louis Armstrong replied simply, "Swing." The concept of riffs "swinging" off and back to a constant backbeat is a given in jazz, and Billy Siegenfeld, a former jazz drummer, has made it the basis of his own approach to jazz dance.

Siegenfeld's Chicago-based company, the Jump Rhythm Jazz Project, embodies that approach. What characterizes its members' dancing is the same impulse that runs through jazz music. Siegenfeld's choreography emphasizes hard-hitting rhythmic precision along with tiffs of rapid-fire variations. The alternation between "hot" and "cool" movement creates a flickering level of visual surprise as movement accents alternate between landing hard on clear downbeats and moving freely on the upbeats that separate them.

Starting life as a modern dancer, Siegenfeld moved in the heady circles of pioneer masters like Martha Graham, Doris Humphrey and Hanya Holm, who pursued their own vision of dance as an art and created a technique in which to express themselves. A graduate of Brown University, he spent nine years in New York, dancing with Don Redlich's company and earning a master's degree in dance from New York University. His was a satisfying career for a time, but by the end of the 1980s, dissatisfaction set in and he began to search earnestly for his own creative voice. The rhythmic pulse of jazz offered an avenue to explore.

In 1990, Siegenfeld founded the Jump Rhythm Jazz Project in New York, later moving it to Chicago, where he's now a professor of dance and music theater at Northwestern University. The Project's ranks were increased to ten dancers in 1997, and the company performs regularly in the Chicago area. Its outreach show, "Jump Rhythm Jazz," is presented in private and public schools in the metropolitan area as well as on tour. Company members, who are as at home in tap shoes as they are in sneakers, pass on Siegenfeld's technique as resident guest teachers in the city's high schools and private studios. They emphasize the basic approach to dance through awareness of rhythm, and they stress percussive expression of energy through all body parts, not just the legs.

Jeannie Hill, the troupe's associate artistic director and a longtime collaborator with Siegenfeld, shares his love of the dancing in Hollywood musicals of the 1930s, '40s and '50s. After they met in a class taught by Robert Audy, a Paul Draper protege, she began classes with Siegenfeld. When they started to appear professionally, one of their first projects was Romance in Springtime, celebrating Fred Astaire and Ginger Rogers as well as a host of other dancing pairs, including the Nicholas Brothers, Fayard (the tall one) and Harold (the short one).

A typical company program of ten dances, all choreographed by Siegenfeld, includes two or three duets featuring himself and Hill. One will almost inevitably be an excerpt from Romance in Springtime; the other works will feature company members. A consistently coherent thematic point of view characterizes Siegenfeld's work: His dances are about something that audiences can connect with. For example, the five-movement excerpt from Romance in Springtime is about two people meeting, missing connections and reestablishing a dynamic relationship, while his Play Dirty is a study of belligerent, streetwise kids.

Among the venues where Siegenfeld has taught classes in his "Jump Rhythm Jazz" technique are the American Dance Festival, Harvard Summer Dance, Italy's Pro Danza, France's Le Festival Internationale de Danse, Germany's Internationale Tanzwerkstatt and Japan's International Summer School of Dance. In 1994, he won a Golden Leo Award for choreography at the Jazz Dance World Congress.

It seems fitting that as jazz music has made its way up the Mississippi from New Orleans toward Chicago, its essential rhythms should inspire a Chicago-based troupe that boasts all the precision and panache of a Louis Armstrong solo.

Dance Magazine writer Don McDonagh is chronicling a decade of the history of New York City Ballet (1957-1967) and is president of Dance Perspectives Foundation.