Final answer:
A temp track is existing music used to demonstrate to the composer the desired style and mood of a film's score, serving as a blueprint for creating the original music.
Step-by-step explanation:
The term used to describe existing music prepared to demonstrate to the composer the type of music desired for the film is known as a temp track. Directors and editors commonly use temp tracks in the early stages of film editing to provide a reference for the mood and style of the score they want for the finished product. Often, the composer is brought in to listen to a temp track as a way of communicating the director's vision and as a starting point for composing the original score that matches the film's unique narrative and emotional needs. Temp tracks play an important role in the film scoring process, serving as a conceptual tool before the final score is composed and recorded.