I would be interested in trying a different approach to this problem.
Namely using machine learning. Would the guitar players on this list
be willing to provide training data? I.e. audio files of you playing
single notes with an additional text file describing the played
pitches. A format like

frame-number start 440
frame-number end

e.g. you have an audio clip at 1000hz sampling rate where an 440hz A
starts on frame 500 (at 0.5 secs) that lasts to frame 2500 (so, 2 secs
duration):

500 start 440
2500 end

This would be an awesome project. I'm very interested. I can provide some training files and a bit of help coding or other supporting tasks. I don't know anything about machine learning, though.