Unison Index referres to the individual voices of a unision stack. Say you have 3 voices unision, then "Unison Index" will have the values -1, 0, 1.
What you can do with it in Odin2 - by example:
1.) Apply tiny filter modulation for each unision voice. If the voices are 100% spread from left to right then you might end up with slightly different filter settings for left and right giving you more sence of stereo.
2.) Slightly detune the LFO frequency for each unision voice giving interesting fx again when he unsion voices are spread from left to right.
I bet this could be complicated in MSF. Anyways ... take it as challenge
