levision rather than filed television, for the sense of immediacy is quite different, and the use of sound in filmed programs follows the rules of the motion picture more than the conventions of television). The image is always enclosed by the framing device of the screen. Chion further notes that there is no corresponding container for sound:
For sound there is neither frame nor preexisting container. We can pile up as many sounds on the soundtrack as we wish without reaching a limit. Further, these sounds can be situated at different narrative levels, such as conventional background music (nondiegetic) and synch dialogue (diegetic)--while visual elements can hardly ever be located at more than one of these levels at once (Chion, 1994, 67-68).
To say we can pile up sounds without limit is technically correct, but we cannot do so and maintain sense or the coherence of any given sound. At some point we reach a mixture that is pure din and otherwise incomprehensible. Still, we do have many more possibilities for communication through sound on several levels at the same time.
As Chion (1994) shows, sound can be classified by its point of origin, its narrative and communicative properties, its means of generation, and a number of other possible criteria. Chion shows how filmmakers adapted to the coming of sound even as they participated in an ongoing argument over whether the silent film should have become the sound film. One group sees the essence of film in the image and downplays the importance of sound, seeing pure filmmaking as conveying all information through the visual image--action, camera movement, visual editing, the juxtaposition of images, and so on. Sound is viewed as something that is added on:
The underlying discourse goes like this: even though the cinema was endowed with synchronous sound after thirty years of perfectly good existence without it, whose soundtrack in recent years has become ever richer...