Midi mapping for turning on/off keys on the keyboard

Is there a way to map a key on the keyboard to the on/off position using Ableton's midi mapping? 

Use case: I want to draw/automate specific notes on the keyboard to turn on/off over time - this lets me create dynamic harmonies and add notes in or take them away over time

Workaround: I have multiple instances of Evoke on the same chain, each with a different selection of keys, and I turn on/off different instances of evoke over time