I've worked on such a program a while ago. It was my "introduction" to
Gtkmm widgets & C++ so the code is really quite poor quality!
The project wasnt completed either, so the "current value" isnt read from
the line. That and MIDI output should be quite trivial to implement, however
I have no experience with CV or other protocols..
Mandatory ScreenShot:
link here
I could post the sources if somebody is interested. I might even work on it a bit myself otherwise.
All the best, -Harry