As far as we know this term was coined by Mackie, but represents a fairly common feature found on modern recording boards. Double busing is like having “Y” cables built right into the mixer. It allows two (or more) multitrack inputs to be fed from one subgroup output. For example, on an 8-bus mixer, when you send signal to subgroup #1 output, it will also send signal to a #9 output. There is no actual subgroup #9, but there is an output that stays tied to subgroup #1 and is controlled by that fader. This allows the recording engineer a convenient way to route grouped signals to more than one destination, such as when using an 8-bus mixer with 16 or 24 track recorders. You simply put the tracks you want to record in RECORD mode, and the other tracks (not in record mode) ignore the signal.