Answer:
<h3>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.[1] 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."[2] 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)."[3]</h3>
<h3>Modern critics disagree as to the exact definition of the concept musical. It is generally agreed upon that in a concept musical, emphasis is placed upon style, message, and thematic metaphor rather than on the plot itself.[4] Thus, the show's structure is rarely cohesive or linear. Critics agree that the most defining aspect of a concept musical is its use of theme. This holistic approach to each show, which focuses on the truthful representation of the theme in every aspect of the final production, sets it apart from other musical theatre forms. Young-Gerber states: "In musical comedy there is no theme. The revue uses a theme to unify disparate musical numbers and specialty acts. The integrated musical contains a theme. In contrast, the concept musical embodies a theme [that is] developed as the musical is written."[1]</h3>
