(1) A method of producing sound motion pictures where the soundtracksound track is recorded on a magnetic tape recorder which is separate from the video recorder and which is synchronized with the movement of the film in the camera, projecting a film with the picture on 35mm film, in interlock with the soundtrack, most commonly on mag film. The synchronization was originally done by recording a special tachometer signal on one track of the tape, but is now done with timecode. Examples of double-system sound are film and Nagra, film and mag dubber, videotape and audio tape.
(2) A film or video production that utilizes sound recorded on a separate tape recorder, such as a DAT or Nagra. This term is still used even if the video recorder is also simultaneously recording the sound. Compare with single sound system. See mut. Also called sep mag.