In the minds of all those who have seen the movie, the script and the song are indelibly linked.
Music has a unique way of characterizing a mood, a time or a place that reinforces our memories.
It also provides polish and pacing. Whatever the medium, it's an additional tool for the scriptwriter. Skillful use requires a knowledge of resources and awareness of its role and limitations. Knowing when music adds to your message or when it detracts is the first concern of the writer. In general, narrative that explains or relates facts can benefit from a musical background.