Using the preamp to duck on the compressor. For example, use a vocal to make the lead guitar decrease in volume when the singer is singing.
TouchPatch: Pre-Out
Insert the Dynamics section on the lead guitar track. Set the threshold to 5, attack to 2, release to 7, classic mode
Run the vocal mic into the preamp and run from the DriveBus out into your system.
Run the XLR output from the Preamp section into the Side Chain input on the Dynamics section.
Now, when someone sings into the vocal microphone, the compressor will 'duck'. Change the threshold to make it duck just the right amount.