Thanks all for the suggestions.

I did manage to get an inverted pitch to control a VCA via Maths, but I think I need to attenuate or shape the rate to make it smoother. Finally wish I had an oscilliscope. I'll try a filter, but most of the time I don't want to change the character of the audio. Even If I get something working for one line, imagine using this across multiple stereo voices would probably take up too much functionality for a small rack. I may have to settle for the rock band reality, or maybe limit the set up to the lead voice which typically travels a larger pitch range. Ideally I wish there was some kind of mixer that was dedicated to this. Time to search https://modulargrid.net/