The word entered the lexicon two years after the release of the first feature length film with synchronized dialogue, The Jazz Singer (1927), and refers to the temporal matching of sound with movements in film and other multimedia images, as when dialogue or singing are matched to lip movements so as to suggest the sound’s point of origin (sounds without a source in the diegesis, the world of the story, such as most film music, are “extra-diegetic”; most offscreen sounds are eventually assigned an onscreen source, thereby extending the diegesis beyond the confines of the frame). Film and media theorists have long argued that sync sound supports realism, a genre of representation many theorists in a range of disciplines have shown rose to prominence with capitalist modernity and both reflects and helps reproduce it. For that reason, the Marxist Soviet director Sergei Eisenstein asserted that rather than “marrying” sound and image for an effect of realism, sound editors should strive to create a discontinuity like that associated with the techniques of “intellectual montage” he developed in silent cinema for joining shots so as to disrupt the apparent continuity of spatio-temporal relations between them. He believed discontinuities could spark new ideas, much as the combination of separate elements of meaning in an ideogram did.

Extending and developing this idea, filmmakers and theorists of experimental cinema have argued for the value of asynchronous sound as anti-realist, promoting critical reflection on, rather than immersion in, the world of the film.  Sound editing points to the way the voice and other sounds tend to divorce themselves from, rather than remain married or synced to, the source from which they originate, a property of language in general, since even so-called “motivated“ or “natural” signs, which resemble or have an existential connection with what they represent (American pragmatist philosopher Charles Saunders Peirce’s “icons” and “indexes”), have a symbolic and arbitrary dimension too, as the differences in onomatopoeias in different languages show. That signs have a metaphoric relation to their referents is a key claim of deconstructive philosophy, which with psychoanalysis and semiotics emphasizes that language is a play of such substitutions; hence shrieking violins can replace the scream of a murder victim in Alfred Hitchcock’s Psycho, or as a more general practice, location sounds are “sweetened” in postproduction, dialogue is replaced through looping (the reverse of “lip-synching”), and some “natural” sounds are figured by surprising Foley equivalents (as when cucumbers and melons are reamed to simulate the noise of bullets tearing through flesh). This denaturalization of the bond between sound and image means that sounds have an uncanny, spectral dimension like that psychoanalyst Jacques Lacan associates with the voice as objet (petit) a. Media theorist Michel Chion terms “acousmatic” any sounds unanchored to a source in the cinematic diegesis and notes their importance in genres striving for an effect of anxiety and horror.