Sound

The SOUNDTRACK of any film is recorded separately from any visual material, and DUBBED over the film at a later stage.

Sound is either:
 * diegetic: i.e. it is part of the STORY of the film itself; or
 * non-diegetic: i.e. it is extra to the story (e.g. background music, voiceover etc.)

Diegetic sound can be either:
 * On- or Off-screen: depending on whether we can actually SEE the source of the particular sound; and
 * On- or Off-mic: depending on whether it is an important, amplified sound, or simply background, atmospheric noise.

Any sound can serve a number of purposes, including:
 * Foreshadowing: i.e. 'warning' us or giving us 'clues' about what is going to happen later;
 * Identification: i.e. acting as the THEME of a particular character, always accompanying their appearance on screen.

If the soundtrack appears to fit neatly and typically with the film, we say it is SYNCHRONOUS. However, if the sound or music is deliberately NOT what we would expect, it is called ASYNCHRONOUS sound.

Finally, the soundtrack and the visual footage usually 'cut' at the same time. However, if we HEAR the next scene before we SEE it (or vice versa) this is called a SOUND BRIDGE, and can make a film flow more fluently, like two pieces of fabric sewn together with a neat seam over the join.

Examples: >