An audio mix bus, often referred to simply as a “mix bus,” is a pathway within an audio mixing console or Digital Audio Workstation (DAW) where audio signals from multiple tracks can be combined and processed together before being sent to the final output or recording. They simply sum different inputs to one output. A bus can be mono or stereo. Mix buses are a fundamental part of the mixing process, enabling efficient handling and creative processing of audio signals within a larger composition. Here are some key points about mix buses:

1. Combining Signals: A mix bus allows multiple audio signals (like individual instrument tracks, vocals, etc.) to be mixed together, making it easier to control the overall balance and feel of the mix.
2. Processing: Engineers can apply effects (such as equalization, compression, reverb, etc.) to the mix bus as a whole, affecting all the tracks routed to it. This is useful for gluing the mix together or creating a specific sonic character.
3. Routing: In a typical mixing session, individual tracks can be sent to a designated mix bus, which can be a stereo bus or multiple buses for different purposes (like drums, vocals, etc).
4. Submixes: Mix buses can also be used to create submixes. For instance, all drum tracks can be routed to a drum bus allowing for collective processing and easier control over the drum sound in the overall mix.
5. Final Output: The mixed audio from the mix bus is typically routed to the master output, where it can be further processed or recorded.