IMPORTANCE OF THE LYDIAN CHROMATIC CONCEPT IN MODAL HARMONY
This is a short but fundamentally important article for musicians who wish to dedicate themselves seriously to Modal Harmony.
The approach to modal harmony and therefore to modal music cannot occur within the framework of a tonal organization based on the Ionian scale, but rather within the framework of an organization based on a Lydian scale.
I believe that the best explanation of this can be given through an example.
Let's start from any Mode, for example C Dorian, which originates from the following diatonic scale: C-D-Eb-F-G-A-Bb.
If this scale is considered within the framework of an Ionian tonal organization, then the originating scale is the Bb Ionian scale: Bb-C-D-Eb-F-G-A. We can note that on the fifth degree there is the F Mixolydian scale, therefore the dominant-tonic cadence, i.e., FVII – Bb maj, exists and consequently we find ourselves in a tonal context; at this point, we cannot speak of a modal context.
If we wish to compose using the C Dorian Mode thinking that it derives from the Bb Ionian scale, we commit a serious conceptual error that will absolutely prevent us from escaping the "tonal cage," the tonal hierarchy and its numerous turnarounds; therefore, the harmonic cadences connected to the Bb Ionian scale will be inevitable because the II-V-I exists in the Bb Ionian scale.
If we wish to compose using the C Dorian Mode thinking that it derives from the Eb Lydian scale, thus within the framework of a Lydian tonal organization, then we will use the scale: Eb-F-G-A-Bb-C-D. As you can see, on the fifth degree there is the Bb Ionian scale and not a Mixolydian scale, so the dominant cadence on the fifth degree to the tonic on the first degree no longer exists. Consequently, the II-V-I no longer exists.
Therefore, if we wish to compose using the C Dorian Mode by conceptualizing it within the framework of Lydian tonal organization and thus thinking of the Eb Lydian scale instead of the Bb Ionian scale, we will avoid the fundamental error and succeed in being mentally free from the rules that govern Tonal Harmony.