There are different types of sound and they all have different meanings. They can be used in different ways to send different messages.
This is sound where the source of the sound is visible in the scene or where the actors can actually hear the noise. For example, a radio playing, voices of people and sounds made by objects in the scene would be an example of diegetic sound.
This is sound that is not visible in the scene and has been edited in for the effect. Examples of non-diegetic sound would be narrators commentary, sound effects and mood music to set the scene and to make the viewer feel more involved.
Subjective sound is like the voice that the character can hear inside their head. It’s just the ‘subjects’ personal thoughts.
Contrapuntal sound is simply a piece of music (usually diegetic sound from a radio or hummed by a character) which sounds like it shouldn’t fit in with the scene. The sound is the opposite of what would be expected and it is used to add effect to the scene. For example, in a horror movie, there would be creepily happy music to make the scene even more eerie than it would be with out it. Other combinations are:
Action with Majestic Music – Inception
Horror/Violence with Happy Music – https://www.youtube.com/watch?v=P0EXHvbsnJ8
The scene from The Shining with the landscape shots is a very eerie scene. If the soundtrack was to be removed from the clip, it would seem to be a very sublime scene. This can be seen in this clip – https://www.youtube.com/watch?v=Uo1C6o3Nr24