First take a look at this slightly confusing table.
|Mode||Tonality||Steps Down||1/2 Steps Down||Interval Down||1/2 Steps Up||Interval Up|
|Dorian||Minor||W||2||Major 2nd||10||Minor 7th|
|Phrygian||Minor||WW||4||Major 3rd||8||Minor 6th|
|Lydian||Major||WWH||5||Perfect 4th||7||Perfect 5th|
|Mixolydian||Major / Dom||WWHW||7||Perfect 5th||5||Perfect 4th|
|Aeolian (Minor)||Minor||WWHWW||9||Major 6th||3||Minor 3rd|
|Locrian||Diminished||WWHWWW||11||Major 7th||1||Minor 2nd|
If you look at this chart you will get a quick reference to where you will find the scale you are needing.
Lets take a example:
Say we are playing a G major chord, we have 3 mode options that might sound good with it. Ionian, Lydian and Mixolydian since they are the 3 "major" tonality modes (that is the 3rd is a major 3rd in the mode). So how do we get to G Ionian, G Lydian and G Mixolydian? I always have an easier time going up an interval rather than down so in the chart above, I have converted the intervals down from the WWHWWWH pattern we talked about in the previous article to ascending intervals.
- G Ionian = G Major, since Ionian = Major
- G Lydian is the major scale starting a perfect 5th above the scale in question. So a perfect 5th above G is D. So G Lydian = D Major
- G Mixolydian is the major scale starting a Perfect 4th above the note in question which is C, so G Mixolydian = C Major.
- A minor 7th above F is Eb. Eb Major is F dorian
- A minor 6th above F is Db.Db Major is F Phrygian
- A minor 3rd above F is Ab. Ab Major is F Aeolian
So now we can grab a mode from a given chord.