Just a thought. Perhaps there’s an easy way to do this already, but I’m very new to Renoise (a few days now) and am going through the manual, and this idea came to mind.
I hope it is at least considered!
You didn’t mention if you are using samples or VST’s?
Because, if you are using samples you have a number of options.
A really quick one would be to add a random LFO to the volume modulation.
Something like this
(tip: set the freq lower than in the screenshot to avoid that it changes while playing that one voice)
Then you could connect a macro to ‘Amplitude’ to control the amount of variation, too.
Stepper device is also relevant
https://forum.renoise.com/t/stepper-bug/44190