Hi everyone,
Yes it is very interesting and most useful.

I do want to generate and indicate the actual notes, as noted above, so that I can create and play a MIDI file.

For my first attempt, I have restricted the fret stretch to the tuning difference between adjacent strings, typically 3 or 4 for guitar, and 5 for mandolin. Obviously, this will vary beween instruments and tunings.

You cannot use a stretch of LESS than this, otherwise some notes are unplayable.

It is VERY tricky to ensure that all notes of a chord are playable and on different strings, when you can't use a chord dictionary, due to allowing custom tunings.

The chords produced so far do not look exactly the same as standard, probably because my algorithm does not yet include two instances of the same note within a chord. (e.g. E3 and E4).

By default, the current effective 'fret window' is frets 0 (Open) to 4. In the next version, I plan to add a user defined 'Window' option and allow barre chords.