Let’s look at the diagram. The Ionian (Major ) mode has a certain number of #’s or b’s. These are always applied in a given order. 1 sharp will be F#. The second sharp will be C#. Flats likewise always are applied in the order Bb, Eb, Ab etc. Place the root note of your choice at the Ionian position. These will be your familiar Major scale root notes, and you will need to know your major key signatures. If you don’t, please memorize them!
Let’s use C as our 1st example.to instantly know what ‘declension’ to apply to change C major (Ionian) to C Mixolydian you move 1 place to the right. For every degree to the right we flatten the Ionian by 1 ‘degree’. Therefore C mixolydian will have 1 flat, and that will be Bb. To find C Dorian, you simply move
once more to the right, and therefore flatten by 2 ‘degrees’. So C Dorian will have Bb and Eb applied to a C root note.
Now let’s take a more complex example. Asked what the notes will be for a B phrygian mode, might take you quite some time to work out, but this kind of task is easy using my mnemonic. B Ionian has 5 sharps. Phrygian demands 4 ‘degrees of flatness’, ( This cancels out the A#, D#,
G#, C#), leaving B Phrygian to be a B root note played with one sharp, F#. (B,C,D,E,F#,G,A,B)
Another example: To play the locrian on A might take some working out, but not anymore! We flatten A Ionian by 5 degrees, so we cancel the 3 sharps and need to add 2 degrees of flatness, so A Locrian will use Bb and Eb only, applied to an A root note. (A,Bb,C,D,Eb,F,G,A)
The exception to this movement to the right is the Lydian mode. This is the mode that demands one move to the left of the Ionian mode on my mnemonic circle. This motion is a move of one ‘degree of sharpness'.
For example C lydian will be one degree ‘sharper’ than the Ionian, so add one sharp F#. To instantly name what the notes are for B Lydian mode, my mnemonic makes it easy. You simply sharpen by one degree, adding the E# to the usual five sharps of B Ionian. B,C#,D#,E#,F#,G#,A#,B