Difference between the three app modes
The app is separated into three modes. You can change them at the top in the navigation bar.
Compose songs and find chords for your songs. Tap in a bar or on a chord in the circle of fifths to start composing. Assign chords from the circle of fifths to a bar.
The circle of fifths will be displayed traditionally. The relative minor chords will be displayed. Chords of a key are not highlighted anymore. This mode is dedicated to learning plain scales. Read more about it.
The circle of fifths highlights the chords of a key. These chords build up a mode. A mode has an associated scale that is displayed in the staff. Accidentals are listed at the beginning, as they would be listed on a score of a song that is written in the selected mode. Read more about it.