In audio engineering, a bus^[1] (alternate spelling buss, plural busses) is a signal path that can be used to combine (sum) individual audio signal paths together. It is typically used to group several individual audio tracks which can be then manipulated, as a group, like another track. This can be achieved by routing the signal physically by ways of switches and cable patches on a mixing console, or by manipulating software features on a digital audio workstation (DAW).

Using buses allows the engineer to work in a more efficient way and with better consistency, for instance, to apply sound processing effects and adjust levels for at a time a workflow known as stem mixing and mastering. Busses are essential to audio production because they help engineers work faster and more consistently. Engineers can apply audio effects and level adjustments to numerous tracks at once and save time and labor by grouping tracks together using a bus. As it streamlines the workflow and aids in maintaining a constant acoustic balance throughout the mix, this can be especially helpful when working on complicated audio projects with many tracks.