Just was playing around with two Arturia vocoder presets which I play with a spilt the last days.
I figured out quite soon, that I get too much bleed from the open mic input into both of the instruments bringing some additional noise within rehearsal.
So I thought about some kind of gate and ended up in a small GP script utilizing Ramp/Generator functions and the NoteTracker 
This is how it looks in the wiring view: a vocoder on the left split of my keyboard controller, and a different one on the right. Both fed from he same mic.
Corresponding rackspace
Function: by default the two Gain and Balance widgets mapped to the two red buttons are muted.
Once a key is pressed the corresponding split gets unmuted, latest key defines the active split.
Once all notes have been released (NoteTracker…) a one shot trigger starts a generator to wait until the release hold time has reached, then both controls get deactivated / the mutes become active. The channels stay open, if other notes are beeping played while in the hold phase, and the on shot gets stopped.
Split point readout is derived from the left split, so the script does not need to be touched when changing the spilt point 
I can now use a head-set in parallel to my main vocal mic on a stand and sing either mic, the vocoder is only “open” once a note is played.
AutoMIDIGate.gig (213.6 KB)
Remarks:
I use an additional Midi In block to monitor the complete keyboard note range.
Sustain is not monitored - latest key release triggers the hold timer…