You know there used to be (maybe still is) a creative writing class exercise where one student was told to go to the board and draw "an animal no one has seen before." When s/he was done, the instructor would point out that what had been drawn was actually just an animal with the head of a lion, neck of a giraffe, tail of a fish, etc.
The point is that no artist can envision something NEVER seen. The best s/he can do is rearrange his or her own reality into a form that seems novel and therefore interesting.
EVERY show is inspired by something. But we have traditionally called a musical "original" as long as its plot is new and not replicated from another medium.
As I'm sure everyone knows and although musical adaptations go back millennia to Greek tragedies, as shows have become more expensive, there has been a trend toward basing musicals on hit films in the hope that a family of four will be more likely to shell out $480 if they already know they like the characters and story. (When reading was more central to our culture, there were more musicals based on books. The same was true, once, of musicals based on plays. Now it's hard to find a play popular enough to draw in a paying crowd for an adaptation.)
Updated On: 9/6/12 at 10:41 PM