Quinterval is an interactive circle of fifths including the display of the corresponding scales.

A key in the circle can be selected either by touching the tonic or by turning the slider in the middle. The circle displays both the respective major and parallel minor scales. The display ranges from F-flat major (D-flat minor) to G-sharp major (E-sharp minor). A second slider can be used to move the visible circle section accordingly.
The note names can be set between german, english or italian notation.

The lower area shows the related major scale with its key signature. The first step and the sixth step with the corresponding minor scale are highlighted. The notes can be displayed with G-Clef, C-Clef or F-Clef. The accidentals can also be displayed before the individual notes.

Additional functionality is available as an InApp purchase:
- Display the notes of the parallel minor scale
- Display triads with their chord names
- Playback notes by tapping on them