Ballet companies, like individual dancers, love to demonstrate how diverse they can be. So New York City Ballet, which began its six-week spring season with eight performances of high modernism (black-and-white costuming, no scenery, most of the music by Webern, Stravinsky and Hindemith), is now giving us a tribute to Broadway, with music by Richard Rodgers, Duke Ellington and Leonard Bernstein. Nobody in New York should be seriously surprised to find such fare at the ballet -- the links between ballet and musical theater have a richer track record here than anywhere else -- but on paper it's still fun to see that City Ballet can give us a program comprising works by three artists who each have been top Broadway choreographers: George Balanchine, Jerome Robbins and Susan Stroman. The two dead choreographers profited on Thursday night from vivid performances: notably from Maria Kowroski's sensational Striptease Girl in Balanchine's ''Slaughter on Tenth Avenue,'' from the 1936 musical ''On Your Toes,'' and young Chase Finlay's touchingly ardent Tony in ''West Side Story.'' An introduction, by the conductor Faycal Karoui, part of the company's See the Music series, entertainingly brought fresh insights into Bernstein's familiar score. [ABSTRACT FROM PUBLISHER]