Why does Musescore interpret Westergaard's A-flat as G? Seeking Clarification on Pitch Spelling

Question

I was reviewing some rules from Peter Westergaard's An Introduction to Tonal Theory. I am really only literate in the key of C major, and so I was notating one of Westergaard's example in MuseScore so that I could then transpose the example into the key of C in order to interpret it. I noticed, however, that MuseScore wasn't allowing me to spell one of the pitches the way it's shown in the text—please see the notes indicated with an arrow in the following images.

My confusion lies with the A-flat note indicated by the arrow in the second image. When attempting to lower this A-flat by a half step in MuseScore, it suggests a G instead. My question revolves around whether the accidental added by Westergaard transforms the repeated note into an A-flat or if it's interpreted as a flattened version of the A-flat note diatonic to the key, resulting in a G.

Despite my limited grasp of enharmonic spellings, I'm hoping to understand if this is a fundamental misunderstanding on my part or if there's a difference in presentation between the textbook and MuseScore.

Answer 1

The key signature includes Ab.

The first example doesn't use any barlines, so in order to notate Ab after the A natural, one needs to use the flat symbol.

The second example notates one note per measure, so any accidentals, like the natural in the third bar, are cancelled in the following measures. Therefore, the flat symbol is not needed in the fifth measure to notate Ab, as the flat comes from the key signature. If you find this notation not clear enough, you can still add a courtesy flat symbol in front of the Ab note. In Musescore you can do it using the flat symbols in "Accidentals" palette. It will be redundant, and it will serve as a reminder for the reader. As the accidentals are not additive, it won't lower the note further, to Abb (or G). You may place the flat symbol in parentheses, for extra clarity.