"Film music" as a term has come to refer to music composed or expressly chosen to accompany motion pictures. The practice of pairing music and image is as old as cinema itself. In fact, Thomas Edison imagined motion pictures as visual accompaniment to the music produced by his phonographs. From the first motion pictures projected to Paris audiences in 1895 to the widescreen, Dolby Digital Surround Sound films of today, music has been a persistent element in the filmic experience. It has been improvised and it has been scored; it has been experienced as live and as recorded performance; it has consisted of both original and previously composed music; and it operates differently from country to country, culture to culture, and genre to genre. The musical, for instance, like the concert film and the musical biopic, has a set of conventions that foreground music. Through all of its various guises, however, film music can be characterized by its expressive power to shape the meaning of the image and to connect the audience to the film.
Film music serves many purposes: it grounds a film in a particular time and place; creates mood and heightens atmosphere; characterizes the people on-screen and helps to define their psychology; delineates abstract ideas; relays the film's theme; and interacts with the images to sell a film economically. Film music engages with the deepest and most profoundly unconscious levels of the audience; it is a crucial part of the apparatus through which a film engages with cultural ideology; and it largely serves these purposes without drawing conscious attention to itself.
Of course, differences in historical and cultural traditions shape music's effect on the film audience. For instance, in the classical Hollywood style, certain of film music's functions have been emphasized over others, giving Hollywood scores a distinctive and recognizable structure. But music's expressive power crosses many borders, and the ability to resonate emotion between the spectator and the screen may well be film music's most distinguishing feature. Films, of course, have various techniques for conveying emotion, including dialogue, expressive acting, close-ups, diffuse lighting, and aesthetically pleasing mise-en-scène . Film music, historically, has been the most reliable and efficient of them. Music embodies the emotion that the image represents, prompting audiences to recognize that emotion and connect to the characters on the screen. Film music thus engages audiences in processes of identification that bond them to the film. The tremolo strings accompanying a suspenseful murder or the pop song heard under a love scene both embody the emotion that the on-screen characters feel and prompt the audience to identify with and share that emotion.