sentences:  The form began to flourish in the late 1960s, with the advent and subsequent popularity of "Man of La Mancha", "Cabaret", and "Hair".Stephen Sondheim, the most prolific author of concept musicals, created "Company" in 1970, bringing the genre to the forefront of the commercial realm.Director-choreographer Bob Fosse and producer-director Harold Prince were equally instrumental in making defining contributions to the concept musical.