violin synth works, sort of... note response too slow, different approach needed?

I hadn't noticed the relationship between b2 and the added ammount thing, well spotted.

I think next time I code something I'll start by looking specifically for relationships like that. I can understand how your idea works, I've pasted it in, will test tomorrow. Some of this sort of thing gets beyond me if I'm getting fed up and dont really want to work on it. In which case I ought to stop and do something else really. Also my maths is pretty poor!

Your are sort of attempting what my friend David Vorhaus started working on 50 years ago (see http://www.unfretted.com/fretless-guitars/david-vorhaus-kaleidophon-an-early-electronic-unfretted-instrument/) he used resistive strips with foil pickup strips. The trick was to "Quantise" the input to digital then reconvert the digital to a correct note and play through ac "correct" analogue frequency source - happy days

That's amazing, didn't realise anyone was building that kind of thing back then. Yes, very similar to mine in many ways.
Of course it means I've found myself 50 years behind the times again. Oh well!