This is not an answer to your specific question about music theory, but I can say in general that the closer you get to the 'correct' key signature entered into your BIAB song, the less likely you will hear notes generated that you think are 'wrong'. It's very common for people to enter a song and forget to change the default key signature of C, but you should. I wrote a sticky post in the Tips and Tricks Forum about BIAB playing notes that are not in the chord you wrote, and some things that you can examine and experiment with to see if it makes a difference. The very first tip is Enter the Correct Key Signature. You can read the article here: https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=694482#Post694482

There is a newer school of thought in jazz arranging that you just write everything in the key of C major and write all the needed accidentals. Personnally I can't stand that; using key signatures gives you additional information that assists in sight-reading and improvising. But if your chart modulates a lot within the range of just a few measures, there is something to be said for it. Just do not try entering the chart that way into BIAB; instead try to change the key signature as many times as needed (F5) to increase the chance of BIAB's accompaniment being pleasant sounding.


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