Moog Theremini has pitch correction allowing it to force your theremin playing onto a chosen key, with a percentage knob (0-100%). I chose instead the Moog Etherwave Plus for the two CV output so I don’t have that feature. Is there a control device out there that can do what Theremini does to correct the pitch?
Obviously, this trick won’t help your control voltages, but this is what it
sounds like when you pitch correct the audio out of an Etherwave: https://www.youtube.com/watch?v=xCSP6pnbefk
(Starts at 7:20)
One easy way to get your Etherwave to control something else in a
chromatically-quantized way is to use a Pitch-to-MIDI converter (and then
ignore Pitch Bend messages).
If you have a modular system, a quantizer will do what you are looking for, there are many available, it takes a smooth voltage in and quantizes it to a chosen scale.