What are the passing notes for each mode - Dorian, phrygian, lydian, mixolydian, and aeolian?
Answer
Great question. First, for those who aren't sure what passing notes are, they are a type of nonchord tone.
The video below introduces the concept of nonchord tones and how to identify them in scales...
There are a number of definitions of passing note, but the most common is perhaps the simplest - a nonchord tone that is played "in passing", as part of a larger phrase, usually before resolving to a chord tone.
So these are notes we shouldn't dwell on or emphasise in our soloing phrases.
Out of the seven modes of the major scale, five can be said to have nonchord/passing notes, based on the "half step rule" outlined in the video...
Ionian (1 w 2 w 3 h 4 w 5 w 6 w 7) - the 4
Phrygian (1 h b2 w b3 w 4 w 5 h b6 w b7) - the b2 and b6
Mixolydian (1 w 2 w 3 h 4 w 5 w 6 h b7) - the 4
Aeolian (1 w 2 h b3 w 4 w 5 h b6 w b7) - the b6
Locrian (1 h b2 w b3 w 4 h b5 w b6 w b7) - the b2
If you want to delve a bit deeper into the theory behind how these nonchord tones were identified, we can look at each scale/mode's related chord and work out where each scale tone lies in relation to a chord tone.
Nonchord/passing tones almost always occur one half step (h) from a chord tone (the exceptions are so rare that this rule can be de facto considered an exact science!)
Ionian
Scale tones: 1 w 2 w 3 h 4 w 5 w 6 w 7
Chord tones: 1, 3, 5 (major)
The 4th lies one half step from the major 3rd chord tone, so that is our nonchord/passing tone.
Dorian
Scale tones: 1 w 2 h b3 w 4 w 5 w 6 h b7
Chord tones: 1, b3, 5 (minor)
As you can see, every chord tone is proceeded by a whole step (w) so there are no nonchord tones in Dorian.
Phrygian
Scale tones: 1 h b2 w b3 w 4 w 5 h b6 w b7
Chord tones: 1, b3, 5 (minor)
The minor 2nd (b2) is a half step from the root (1) and the minor 6th (b6) is one half step from the 5th chord tone, so the b2 and b6 are the passing tones.
Lydian
Scale tones: 1 w 2 w 3 w #4 h 5 w 6 w 7
Chord tones: 1, 3, 5 (major)
All chord tones are proceeded by a whole step, so no passing tones in Lydian.
Mixolydian
Scale tones: 1 w 2 w 3 h 4 w 5 w 6 h b7
Chord tones: 1, 3, 5 (major)
All chord tones are proceeded by a whole step, so no passing tones in Mixolydian.
Aeolian
Scale tones: 1 w 2 h b3 w 4 w 5 h b6 w b7
Chord tones: 1, b3, 5 (minor)
The minor 6th (b6) is one half step from the 5th chord tone, so that is our passing tone.
Locrian
Scale tones: 1 h b2 w b3 w 4 h b5 w b6 w b7
Chord tones: 1, b3, b5 (diminished)
The minor 2nd (b2) occurs a half step from the root (1) so that is our passing tone.
You can use exactly the same process for identifying nonchord/passing tones in other scales.