Incidental music is music that is used in some other media or situation that is not primarily musical, such as a movie, television program, radio program, religious service, television or radio commercial, stage play or video game. Incidental music's functions can include indicating the start or end of a performance, serving as background music, enhancing the telling of a story and serving as a filler during a change of scenes. Its use dates back at least as far as ancient Greek drama, and many classical composers wrote incidental music for various plays and other uses. Some music originally written as incidental music by classical composers has survived independently and become part of the standard repertoire of concert music.