Ribbon controllers and breath controllers output a continuous voltage for pitch and usually a pressure threshold gate indicating note on. If you quantize the continuous voltage it just makes a glissando effect which destroys the expressiveness of the controller. Ideally, the quantizer would lock into scale at note on but then allow pitch bend and vibrato freely.
This can be patched with a quantizer, sample & hold, and two precision subtractors. Simply sample the continous voltage at note on, and output the difference between a quantized copy of that sampled voltage and the change in ribbon position since note on.
v/o output = quantize(sample(ribbon pitch, ribbon gate)) - (sample(ribbon pitch, ribbon gate) - ribbon pitch)
https://modwiggler.com/forum/viewtopic.php?p=4210901#p4210901