Dubbed the ‘Wheel of Truth’ by Wr4thTV, I originally conceived the mode wheel as 2 paper discs connected with a split pin. This is how I visualised the diatonic modes and used it determine relative modes of a scale. 

On the outer disc, the seven diatonic modes – Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian, and Locrian – are arranged in a clockwise manner. The inner disc shows the 12 notes of the chromatic scale in a counter-clockwise order.

To use the mode wheel, pick your starting mode by spinning the outer wheel and your key by spinning the inner wheel. Once you have these you can spin the entire wheel to see the relative modes.

I found the mode wheel to be particularly useful during improv sessions. In such sessions, we would often be given a random key and mode to play in. For instance, we might be asked to play in G Mixolydian. While this might sound confusing at first, a quick glance at the mode wheel can tell us that G Mixolydian is equivalent to A Aeolian, which is a mode that most musicians learn early on.

Being able to quickly determine the relative modes of a scale has helped me to improvise better and explore different musical ideas as I could more confidently switch positions on the fretboard. It has also helped me to understand the relationships between the different modes and how I can use that in my playing.

Overall, I feel the mode wheel is a useful tool for those looking to gain an understanding of the modes and scales, and particularly for those learning to improvise.