Film music can be divided into two categories:
Music contained within the action is usually referred to as diegetic music. It is included in the story, eg music heard on a radio. Most film music is non-diegetic.
Background music is often referred to as underscoring. It adds to the mood of the scene, reinforcing dramatic developments and aspects of character.
Music is an important part of film. Film music serves to:
When the music is precisely synchronised with events on screen this is known as Mickey-Mousing, eg someone slipping on a banana skin could use a descending scale followed by a cymbal crash. Mickey-Mousing is often found in comedy films.
In a film score, the orchestration (Organisation of musical instruments for an ensemble performance) and instrumentation (Particular type of instrument used in a music) can be very important.
Instrumental colour can suggest images, eg bagpipes evoking Scotland or muted brass suggesting something sinister.