Mainstage Midi send Possible?

I am trying to have a Patch per song in our live set. I'm pressing a foot control (momentary) during the chorus and break to layer another synth on top of the main synth. right now i've programmed that foot switch to just "un-mute" the channel that contains that synth. Problem with this is that the sustaining sound cuts off when i go back into the next verse after letting go of that footswitch. Is there any way to do this?

Thanks!