In the days of silent film, the only methods to express how a character felt were the dialog cards, the actor’s face, and the music score, all of which worked together to convey the necessary emotion. In a silent film, if a character delivers what appears to be a tense or dramatic speech, tense and dramatic music is sure to accompany it. In modern filmmaking, the same can be said to be true.
Music score is a basic and effective way to heighten the drama of a given scene in a film. Regardless of the genre (drama, comedy, romance), a film score can add to nearly any scene. In an action set-piece, the music will match the action in terms of power and intensity. In a comedy scene, the score can be expected to be as light or silly as the action taking place within the scene.
At the beginning of a movie or scene, music is often used (along with establishing shots) to help set a tone, before any dramatic action takes place. In the beginning of a horror film, shots of a desolate, empty street may have ominous, foreboding music accompanying them, to establish that the action about to transpire is very scary.
In many period pieces, film score or music from the era is used to help establish and reinforce the specific time period which the move is set in. Example: A film set in medieval times, will often use source or score music from the very era that it is trying to recreate, thus further embedding the viewer within a particular time and place.
The music montage is a popular way to condense a large amount of information into a short amount of time. The use of a pop song or score selection, accompanied by thematically related shots (the lead character is sad, people falling in love, hero in training) advances the story without spending the days, months, or years it would take in real life for the actual events to transpire.
Musical misdirection is most often employed in, but not limited to, thriller and horror movies; usually to lull the viewer into a sense of complacency before a big scare. Example: The heroine babysitter walks into the upstairs bedroom as calm music plays, only to discover a killer behind the door, immediately cued by pierced, shocking music. In an opposite example, the babysitter walks upstairs, with tense and scary music underneath the scene, expecting to find a killer, when it turns out only to be the house cat.