Understanding Buses, Subgroups, Auxes, VCAs and Groups.

Bus: any kind of audio signal path that allows the combination or “summing” of different signals to be routed/processed together.
Subgroup: a grouping of instruments or tracks that are mixed or inserted into the “main” mix as a composite signal.
Auxiliary track: a type of bus for creating auxiliary mixes or common parallel processing.
VCA (voltage-controlled amplifier): a voltage control source that acts as a master control over the volume levels of the channels in the VCA group. VCAs do not pass audio.
Group: the linking of certain user-defined functions, notably level, between tracks (other options include editing, automation, alternative/playlist select, panning, solo, mute, and record arm).

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