When I change unison values I get an audible click. is there a way to prevent this?
there would need to be some kind of windowing or interpolation built just for that. hard to imagine how that would be done.
There is not. It would be an expected behaviour as changing the voices up or down will have a new voice starting (or ending) it’s waveform, which causes the click (excuse my mediocre explanation)
You can try changing the random phase amount to see if this may lessen the clicking sound when the voices are coming in. Otherwise if you are looking to have a part in your track switch unison voice amounts I would recommend having either separate patches, or maybe get creative with having a new oscillator come in with volume automation/LFO (depending on your original patch). Just some ideas in case it helps!
Edit: at work so I can’t test but maybe try a higher quality setting in Vital? Not sure if this would do anything but mebbe worth a try.