Hi Dave
Assignable buttons are not designed for this task. Basically you have two options:
- use a registration to switch the mic effect
- add MIDI events to the file to switch the effect at the end of bar 12
As you asked for a button for switching, here's the idea how to use a registration. I assume the mic setup uses the system reverb and the mic insertion effect is set as a delay effect. Upon loading the MIDI file, the mix for the mic should be set to Reverb=0 and Insertion Effect Delay = [some value as needed]. Then you can swap the values, Reverb = [some value as needed], Insertion Effect Delay = 0 and store this in a registration, tick group Vocal Harmony/Mic Setting.
HTH
Michael
Edit: "mix for the mix" was obviously nonsense, corrected to "mix for the mic"