What is a 'sound bus' and how is it used in a film mix?

• A. A bus is a routing path that groups multiple tracks for collective processing and easier control (e.g., dialogue bus, music bus).
• B. A physical bus used on set for distribution of power.
• C. A type of digital compressor.
• D. A separate room for mixing.

Answer: (A)

A bus in film mixing is a routing path that groups several tracks so you can process and control them together. In practice, you route related elements—like all dialogue tracks to a dialogue bus, all music to a music bus, and all sound effects to an effects bus. This lets you apply the same compression, EQ, or other processing to the whole group at once, which helps keep level and tonal balance consistent across the scene. It also makes automation easier, since you’re adjusting one fader for the whole group rather than many individual tracks. Buses can also feed into other buses, such as sending multiple tracks to a shared reverb via a reverb bus, before the final mix passes through the master. So the idea is that a bus is a collective routing and processing pathway, not a physical device, a compressor, or a room.