Concept musicals were first introduced in the 1940s, though two shows compete for the title of 'first concept musical:' Allegro and Love Life. 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. Modern examples of the concept musical include Assassins and Avenue Q. Shows ranging from Fiddler on the Roof to Sweeney Todd have been argued as being concept musicals, though there is little critical agreement.
The concept musical has direct ties to the megamusical, which has similar roots in the Andrew Lloyd Webber work Cats, and the similarly plotless revue. Mirroring the social upheaval of the 1960s and beyond, the concept musical as a form provided a means of expression and experimentation for musical theatre writers and audiences alike.
“The term 'concept musical' did not appear in theatrical scholarship until after 1970, when the phrase “conceived by” preceded Michael Bennett’s name in the A Chorus Line billing. Most theater historians agree that the terms 'concept' and 'musical' were not linked until 1968, in a New York Times review of Zorba by critic Martin Gottfried. Referring to Harold Prince's direction rather than the show itself, Gottfried wrote: "Conception is the big word here - it is what is coming to replace the idea of a 'book'... there is even less room than in the usual musical [for story] because Prince's concept... apparently won out on every question about cutting." In a later review of Sondheim's Follies, Gottfried defined it as "a show whose music, lyrics, dance, stage movement and dialogue are woven through each other in the creation of a tapestry-like theme (rather than in support of a plot)."