What are the functions of music in films?

Ever since the dawn of cinema, films have had an incredible ability to delve an audience into a world that differs from theirs; containing interesting characters, locations or special effects. In this sense it can be used as a form of escapism from a monotonous lifestyle, this can be demonstrated more effectively in sci-fi or fantasy genres, as the audience is transported to a universe that transcends reality, in some cases. Some examples of this would be Star Wars, or The Lord of the Rings. However, movies need something else other than the actor's emotions to set the mood to a scene- an accompanying soundtrack.

Before the 'talkies', movie directors were unable to capture any sound within a scene, instead, cinema owners would employ the aid of a pianist who would play a set of written music created by the movie producers to set the mood of a scene, and in most cases, emulate the actions of a character.

Eventually, when sound recording was implemented into movies, a live pianist was no longer necessary, as full orchestra soundtracks could be edited into a movie through post-production, allowing directors to tell a story more effectively.

In many cases, the soundtrack of a movie can tell the story by itself; often the audience will base a conclusion on a character's personality or intentions by the mood of the music- often a darker sounding track can make out a character to have evil intentions:

 Or, the soundtrack can be used to portray a character as enigmatic, and ethereal:

The elves in The Lord of the Rings are described as wise, and mysterious. Their character would be extremely difficult to convey had they lacked the accompanying soundtrack.

Obviously, the composer of a soundtrack requires a track from another film as a basis of inspiration. Often the track will be used to see if it conveys the correct emotions, this is called a 'Temp Track'.