XML has incomplete voices - very hard to get rid of in MuseScore

Hmm, I'm not sure what you mean when you say you are "glad that's fixed". I wasn't describing something that has changed recently; it's *always* been the case that edits to one measure don't affect others. The only time adding a note to one measure would run into the next would be if you in fact *entered* a note that doesn't fit in the current measure (eg, trying to put a whole notes on beat 4, which makes no musical sense). So again, if you are having a specific problem in this area, we'd really need to see a specific score and precise steps to reproduce the problem.

As for the examples you did provide:

In American Pie, I do see a whole lot of spurious key changes that SharpEye apparently created, going back and forth between G and C when it should presumably stay in G. I am furthermore guessing that you are attempting to delete the *courtesy* key signature that is correctly and automatically added at the end of the *previous* system, rather than dealing with the *actual* key change which occurs at the *beginning* of a system. You are more or less on the right track to observe that the courtesy key signatures at the ends of the systems "actually don't exist". They *do* exist, but they aren't the real change - the real change is at the beginning of the enxt system, according to standard rules of notation. The courtesy changes are automatically generated (again, according to standard rules of notation) only if the measure before the key change occurs at the end of a system. So, again don't delete those, you need to fix the *actual* key change at the start of the next system.

Deleting the actual key change is easy enough for the changes from C to G - select the actual key change at the beginning of measure 38 (for example), press delete. This automatically removes the courtesy change at the end of the previous system as well. However, for the changes from G to C, there is nothing there at the beginning of next system to select in order to press delete, so instead, simply *replace* that with a G major key signature.

Rather than fix each of these errors one at a time, however, a much easier way would be to do them all at once. Lots of ways to do this, here's one: right click the initial key signature, Select / All Similar Elements, then Ctrl+click that initial key signature to deselect it while leaving the others all selected. Hit Delete, and everything is in G major as it should be.

As for the extra time signature in "Mrs. Crandall", you can delete that by simply selecting it and pressing Delete. Changing time signatures removes line breaks because the barlines they were originally attached to no longer exist after a time signature change, but you can simply add them back.

Back to the original topic of voices:

Also of this said, it is definitely the case that while MuseScore provides powerful tools for editing scores, most of those tools are optimized for correcting the sorts of mistakes people make entering scores themselves or for changing their mind about how to notate something - changing from one correct notation to a *different* correct notation. Softeware like SharpEye often produces scores that are pretty whacked out, filled with more numerous and more serious errors than the sorts of things that otherwise happen normally. I can certainly see that correcting a score created by SharpEye would be an adventure. So it is definitely worth showing some of these sorts of examples in a feedback session - assuming you are still up for doing that - and hopefully that can help give us ideas for how to further optimize the editing tools to handle these more extreme situations.

If you check measure 54, you will see that it is *already* an F natural, because the key signature at that point has no flats or sharps. So it was already an F natural, and it stays F natural unless you change it. Changing the key signature does *not* change any notes already present - and in most cases, you wouldn't want it to. SharpEye entered an F natural, and MuseScore assumes you want to *keep* it an F natural even if you decide to alter the key signature. Which is to say, it very explicitly does *not* try to "reformat" or make any other unnecessary changes to your score. The notes you (or SharpEye) entered stay exactly as they were. If you want to change those notes, you will need to ask MuseScore to do so - it won't change them unnecessarily without your explicit instruction to do so.

One way to get MuseScore to change all notes *not* in the key into notes that *are* in the key would be to select the passage, Alt+Shift+Up to transpose everything diatonically up a step, then Alt+Shift+Down to transpose everything diatonically down a step.