The screenwriter as orchestral composer

A screenwriter was like someone presenting a hundred folders of sheet music to an orchestra, with not only the parts for all the instruments charted out but how their harmonies and counterpoints worked as well, how they all went together, how loud they'd play and how soft, how fast, how slow, accented and muted, with a final file handed to the orchestra's conductor, whose job it would be to make sure those hundred performed in unison.  ~Marc Norman, "What Happens Next"