Sound and Music

Sound and music are used within film to reinforce the atmosphere of the scene. This therefore enhances the audience's emotional experience by suggesting a character's thoughts and feelings by the genre of music or type of sound. Furthermore, sound and music can be used to build a sense of continuity by using techniques such as sound bridges which allow two scenes to run seamlessly from one to the other. 

Diegetic sound refers the sound within a scene. Despite not being able to see the source of the sound, as long as it's relative to the scene, it can still be diagetic. 

Non-Diegetic sound is sound that comes from another scene, like when sound bridges are used, where they do not relate to the action within the current frame. Theme songs and voice overs are also examples of non-diegetic sound.

When the sound is from a contrapuntal source it makes the sound track contradict the image track and can be used to give a humorous effect.