sentences:  Director-choreographer Bob Fosse was a key figure in the further development of the concept musical.After directing the film version of "Cabaret", Fosse helped to shape the 1972 Broadway musical "Pippin", written by Stephen Schwartz and Roger Hirson.Fosse’s conceptual vision for "Chicago", which opened on Broadway in 1975, featured vaudeville routines that "comment[ed] on the system of justice and imprisonment in Chicago in the 1920s... Kander and Ebb and Fosse and Prince were advancing upon the convention by which characters have two modes of existence in musicals.