I have found a bug in HARMONY which occurs in uncommon situations when generating an accompaniment. (Options "Generate notes and Chords" and "Generate notes from chords")

The program attempts to keep track of accidentals in a bar, and adds 'implied' ones so that it can play them correctly. Sometimes, though, it will add an 'implied' accidental to the melody, which is obviously not correct, and which changes the tune.

This will be fixed in the next version, 3.4.3, which I hope to upload to my web site next week (around 1st October). This will be an upgrade rather than a full install.

In the meantime, there is an easy workaround. On the Options menu, select "Show implied accidentals". These will then be displayed in red on the score. You should then change these notes by adding an explicit natural to the note (either by drag and drop, or by the edit menu). This will correct the playback, and will also prevent the note from being changed if you generate the accompaniment again.