Incidental music is music in a play, television program, radio program, video game, film or some other form not primarily musical. The term is less frequently applied to film music, with such music being referred to instead as the "film score" or "soundtrack."
Incidental music is often "background" music, and adds atmosphere to the action. It may take the form of something as simple as a low, ominous tone suggesting an impending startling event, or, to enhance the depiction of a story-advancing sequence, such as its use in the film The Insider. It may also include pieces which will provide the main interest for the audience, for example overtures, or music played during scene changes, or at the end of an act, immediately preceding an interlude, such as in the classic television series Star Trek (as well as in the other Star Trek television series). It may also be required in plays that have musicians performing on-stage.
The use of incidental music dates back at least as far as Greek drama. A number of classical composers have written incidental music for various plays, with the more famous examples including Ludwig van Beethoven's Egmont music, Franz Schubert's Rosamunde music, Felix Mendelssohn's music for A Midsummer Night's Dream, Georges Bizet's music for L'Arlesienne, and Edvard Grieg's music for Henrik Ibsen's Peer Gynt. Parts of all of these are often performed in concerts outside the context of the play.
Modern composers of stage music include John White. One of the best known incidental music composers for British television is Howard Goodall, who wrote music for The Gathering Storm, Blackadder, and Red Dwarf, as well as the film Bean.