Parallel audio recording locked to picture timecode during production — synced playback for editorial and dialogue. Industry standard for post-sync reference.
On set, the sync track runs parallel to the camera — a dedicated audio recording coupled to the camera's image and reference microphone via timecode. The sound assistant or boom operator uses a portable recorder (Sennheiser MKE 600, Rode NTG series, or professional digital recorders like Sound Devices MixPre-3) to capture the primary audio signal with higher quality and better control than the built-in camera mics. This track is the foundation: it stores the dialogue, the location's atmosphere, the actor's performance — unadulterated and independent of the camera's raw footage.
The technical coupling is achieved via timecode sync, ideally jam-sync to the camera or via clapperboard and manual marking. On set, you work with multiple tracks: main microphone (lavalier, headset mic, or boom), wildline channels for atmosphere or backup, and often direct XLR outputs from wireless receiver units. The recorder runs from the first sync to the cut — without interruption, to avoid sync issues in the edit. This is the distinguishing feature compared to the camera reference track, which is usually compressed and noisy.
In the edit, you do the following with it: The sync track is imported into the NLE, aligned with timecode, and used as the base audio track. The dialogue editor works from this to create the clean sound, cuts out silence, and removes breath sounds or tape hiss. The track also serves for synchronizing multi-camera shoots — each camera has its timecode, but all run to the same sync track. If something goes wrong (wireless dropout, boom pop), you still have the camera reference as a fallback — but never the other way around.
Common mistake: The sound assistant stops recording between takes. You should absolutely avoid this. Continuous sync track means: Start cameras → Start sound → Let it run until the end of the scene. Even takes where only the AD is speaking or the camera is loading are recorded — editing room luxury that you'll need later. The track is not just working material, but also proof of performance: for questions about the original performance, it provides objective documentation.