Sound whose source is not visible in frame — off-screen dialogue, music, ambient noise beyond the camera's view. Opposite of sync sound.
You're sitting in the editing room and quickly realize: sound makes the film. Hors-son—that's sound whose origin lies outside the visible frame. The voice of a narrator who is never seen. The siren wail from the street, even though we're sitting in a closed room. The orchestral music that no music box or orchestra in the frame explains. The opposite: In-sound occurs when the source is present in the frame—a speaking person we see, a radio that's on and visible.
Practically, hors-son becomes an essential tool of cinematic language. On set, you often only need the shot of the speaking person for dialogue—you cut in the other person's response as hors-son while their face reacts. This is called shot-reverse-shot in sound. Spatial continuity also arises through hors-son: you show a character on the street, cut in bird sounds, distant traffic noise—suddenly the location feels alive without a camera having to capture every sound source individually.
In editing, hors-son becomes a dramatic weapon. Silence breaks, an invisible voice speaks—attention immediately focuses. The audience fills the gap with their own imagination, which often has a more powerful effect than being shown visually. Think of documentaries, voice-overs, or thrillers: a voice from off-screen creates distance, builds suspense, can depict an inner monologue. Sometimes it's just a practical solution—if the speaker's mouth isn't synchronized with the sound, you cut the voice as hors-son and have them remain silent in the shot.
Important: Hors-son is not automatically made invisible. It is consciously or unconsciously out-of-frame, but fully present in the sound mix. You mix it equally with in-sound. The viewer trusts your sound design. If a sound suddenly appears that no one can explain—that can disturb or deepen, depending on how you use it. In blockbusters, hors-son masks technical limitations; in arthouse productions, it becomes an artistic statement.