its working well.
i setup the sounds on tracks 1 to 4 as nice bass tone with different filters, panning etc.
trigging them via 1 x midi channel (instead of 4).
cable is set to volca fm mode , 'polymux' 4 notes , so basically every time 1 note goes in it cycles around channels 1 to 4.
if i hold a 4 note chord it'll play them all together. (so you could fine tune each sound to be offset/filters, delays,reverb , envelope .. like a 4 note synth with independent envelopes etc.
if you hold 2 notes it'll switch between 1/2 , 3/4
not sending any sync , program change , just note data.
on the track i'm messing with , 4 other internal channels are bass/drums etc.