You can attach a modifier to the Mix parameter on the Looper block, which is the mix of your live playing against the looper volume. There is also a Dub Mix parameter (that can also have a modifier), and that controls the balance of each overdub against an existing loop recording.
Generally speaking, controlling a mix parameter would be best suited with a knob or expression pedal. You can hook up to 2 expression pedals to the MC6+, and of course you have all the pedal inputs on the Axe itself.
But it sounds like you're looking for a footswitch solution. The easiest setup is to use the "Control Change Toggle Value" MIDI Type on the MC6+. On the Axe, choose which "External Controller" you'd like to use. Let's assume you choose External Controller 5, because 1-4 are usually used for Axe/MFC pedal ports. Let's also assume you keep the CC assignment for External Controller 5 at the default, which is CC #20.
On the MC6+, create a preset and call it "Looper Level". Start with these settings:
- Type = "Control Change Toggle Value"
- Number = 20
- V1 = 0
- V2 = 127
- Channel = 1, assuming you've left Axe MIDI channel at the default
On the Axe, edit the Looper Block and page over to the Mix tab. Select the Mix parameter and hit Enter to add a modifier. Start with these modifier settings:
- Source = Extern 5
- Min = 40%
- Max = 50%
- Damp = 500ms
- leave all other parameters at default (or adjust as desired)
What this will do is create a footswitch on the MC6+ that, when pressed, will cut the Looper volume by about 2-3dB or so. It will smoothly fade to the new volume (that's the Damp setting). When pressed again, it will fade to the original volume. You can adjust the Min and Max values of the modifier to taste. 50% is the default looper mix, which means the loop is as loud as the live signal.
You could also run the Looper block in parallel to your main path on the grid, set the Mix at 100%, and attach the modifier to the Looper Block Level parameter instead.
If you were actually looking for an expression pedal solution, then you can hook your pedal up to the MC6+, and assign it to CC# 20 instead of creating the footswitch preset above. The Axe modifier settings would be the same, although you would set the Damp parameter to 0ms if you want the volume to respond in real time to your pedal movements.
