The harmonic scale arranges all of the chords available in your chosen key in to a specific order that promotes natural strength and flow. Unlike other scales, such as the major or minor scale, the harmonic scale prioritizes the flow and movement of chords, not individual notes.
Using the Harmonic Scale to come up with powerful and creative chord progressions is easy, when you know a few simples rules:
The strongest relationships are found by moving around the circle in a clockwise direction from one chord to the next. (e.g. in C major moving from C to F, F to Bdim, etc)
The second strongest relationships are found by moving either clockwise or anti clockwise to the next but one chord. (e.g. in C major moving from C to Bdim or Dm)
The third strongest relationships are found by moving to the opposite site of the circle, the next but to chords in either direction (e.g. from C to Em or Am)
Moving anticlockwise except directly to and from the root chord doesn't generally sound good. Try and avoid it.
The background colors on the wheel are designed to try and help you remember these rules. From your currently selected chord (the darkest pink) backgrounds are shaded from darkest (strongest relationship) to lightest (weakest relationship).
Using the Harmonic Scale and sticking to these rules - you should be able to come up with some new, creative chord progressions for your next song!
For further information and a more detailed, technical explanation of the Harmonic Scale please see our blog post: Understanding the Harmonic Scale: Creating Natural Flow in Chord Progressions