Music is used in documentaries for many of the same reasons it is used in feature films. Generally, it is used as incidental or background music to help produce an appropriate emotional response from the audience. As the music does not form part of the narrative it is considered to be 'non-diegetic'. Therefore, much of the time music goes unnoticed by the viewer and works at a subconscious level, 'telling' us how to feel.

At another level the music can help to shape the narrative by - for example - rhythmically determining the length of cuts in the visual material. This is particularly the case where there is no spoken narrative and still images are used  and therefore of indeterminate length. Where a piece of music is specifically written for documentary this can also lead to a more 'artistic' use of music in the film.

Occasionally, as shown in some of the examples provided here, the music can form an integral part of the narrative, becoming 'diegetic' as it lyrically or musically adds to the message being conveyed,