Watch the Technique 2 online guitar lesson by John Stowell from Modern Chord Melody
Technique 2 The whole notion of substitutions and layered harmony has interested me for a long time. Labelling components of the harmony is an efficient way to understand all of the necessary applications and ultimately have an intuitive feel for how to use extensions/tensions creatively and spontaneously.
Just as the major scale has 7 modes that outline important harmony, so do the melodic and harmonic minor scales. I'm more comfortable with the melodic minor modes, but that affinity may be a reflection of the fact that I've spent more time with those sounds than the harmonic minor modes. I'm slowly warming up to the latter.
Because the melodic and harmonic minor modes are more complex sounding than the modes of the major scale, I've found that an easier and faster way to internalize these sounds is to think of the melodic/harmonic minor scales/arpeggios/chords in different keys layered of the basic harmony of a chord. For example, as I mention in this video bank, rather than thinking of using the 7th, 2nd, 4th and 5th modes of the melodic/harmonic minor over a dominant chord, an easier way for me to digest this theory is to think of melodic/harmonic minor scales a half step above, whole tone below, 4th and 5th above the original dominant chord. The trick here (as with any substitution) is to learn to move fluidly back and forth between the basic sound and the substitution so that you can control the amount of tension in your lines. In the case of the dominant chord, the altered sounds (raised and lowered 5th and 9ths) can be used to move away from and back to the original sound if the chord isn't functioning as a V chord, or to create resolution if the dominant chord is a V moving to a I.