I'm still working on a viable guitar controller for my modular synth and have now got a pretty good working setup that is now being built up into a finished module. It uses the EPE guitar to MIDI converter, and feeds this into an Arduino MIDI to CV/trigger/gate converter. In addition I have some momentary and latching switching to give synth only/synth+guitar/guitar only. The CV holds precisely and the envelope length is totally independent of the guitar envelope - so infinite sustain is possible. I can play a synth note, then switch to guitar and play over the pedal note. A whole new world of sounds and possibilities. Some minor tweaking required, but I'm now keen to get it operating as a complete build rather than on the breadboard.

I was never convinced enough to commit to building the Penfold guitar tracker - It had promise, but was very glitchy and in reality not very useable form the videos I'd seen. I think a real breakthrough with the Penfold circuit can be seen here; https://www.youtube.com/watch?v=5IdbPmj7BYc. I think it sounds pretty good. The only real downside now is S&H droop - not evident from the clip, but any circuit that uses a switched capacitor to store the CV suffers from this problem and it limits the note length before the pitch drops too much. In practice though, this may not be a problem as it's more than made up for by the tracking and lack of any serious latency.