Ok. I know I said I was done but this one keeps bugging me. The inspector has some usability inconsistencies just within the inspector and compared, generally, to other Windows apps.
Could you have an OK and Cancel button in the Inspectors? I always find myself mousing to the bottom and then going up to the top to click the little red X. OK and Cancel buttons, for one thing, would be bigger than the little red X but they are also just where we go by habit. And it would overcome the issue that I regularly lose my string and fret count setting changes because I forget to apply them individually. An OK button at the bottom to apply all my changes would be more standard and really make the app perfect.
I know that these suggestions are not huge issues. It speaks well of the work done so far on the app that the suggestions I have made are the biggest problems I found.