Music in the movies is an important part of the filmmaking process, and is one of the factors that determine box office success or failure. If you think about it you'll begin to understand the value and contribution of music and lyrics to film. Whether you are a producer, director, agent, composer, songwriter, studio executive, music supervisor, business affairs executive, film student or anyone involved in film or who wants to be in film---you need to know what type of music you are looking for, what the music intends to accomplish, how you license or acquire it, how much it will cost and how much it will earn.
Types of Music in Film
There are three basic categories of music for film: underscore, pre-existing song, and songs written specifically for the film.
An underscore is what many people think of when they imagine music in film. Underscores are usually composed for an orchestra of various sizes to perform, however, many are now also written for electronic music and MIDI sequence as well.
The pre-existing song is simply a song that is already written and is often already familiar to the public. It is common for a director or writer to use a song because they imagine it playing during specific scenes while writing and shooting or they feel that it will set the perfect mood for the shot.
A song that is written specifically for a film is just that, and often includes lines about the characters or plot of the film, or it is simply written to convey a message during the film. This type of film music was especially popular when musicals were being frequently written.