Oh, I thought it'd just be a matter of adding an command interpreter option for Voicing Mode=XX, which is very simple. Now you want the code to go with it as well ... not so simple.
BTW, we are talking about 2 different issues: The harmony links (I think) would apply to the Harmony settings for Solo tracks; Voicing MODE is for chord tracks. Chord Voicing is another (complicated) kettle of fish.
One of the problems with the way MMA operates is that it really has no knowledge sharing between tracks ... so when it is creating the Solo-1 track it doesn't know about the Bass-Guitar track (matter of fact, the order of creation isn't even known). So any harmony must be developed inside a specific track on a standalone basis. Now, when doing this, the CHORDs are known.
So, doing a harmony for a solo track is, currently, a simple matter of looking at the notes in the chord and the current solo note and grabbing something appropriate.
Following some "better" rule than "use a note from the chord lower than the melody note" could be done. I'll add it to my TODO. And, thanks for the links ... I'll give a read later.
BTW, don't forget that there is nothing preventing you from having 2 (or more) solo track, each with different notes and voicings in which you set the harmonization for each line. Oh, you wanted a computer to do that for you
Honestly, for really good arranging, you really need to do it with paper, pencil, a keyboard, sweat and love. But, computers might be useful
