Soundtrack

1. A recording of an original score or a collection of songs from a film. While always a part of movie-making, soundtracks became increasingly popular in the late 1980s and early '90s as another form of film marketing.

2. The recorded sound of a film, which includes dialogue, background noise, sound effects, and a musical score. Magnetic soundtracks, like the kind used for an average cassette tape, have the sound encoded on a magnetic strip attached to the film stock. Optical soundtracks, however, use a beam of light to create a band on the stock that widens and narrows in order to encode the sound signal.

sound effects

Natural or artificially created sounds, other than speech or music, that become part of a motion picture's sound track. Such sounds (a gun popping, a door slamming, a glass breaking, thunder rolling, etc.) are recorded during filming or separately (sound not recorded synchronously with film is known as "wild sound") or borrowed from a library of stock sound effects. Certain large film and TV studios are equipped with a sophisticated sound-effects console that stores hundreds of prerecorded sounds and enables the operator to scan, locate, and introduce directly into the sound track any desired effect within seconds. See also effects track.

voice over (abbreviated V.O. or v/o)

Narration or dialogue spoken by a person not seen on the screen at the time his voice is heard.