TONAL CENTERS – 2nd PART -
“TONAL CENTERS” IN MODAL HARMONY
As already stated, the term “tonal center” is a generic conceptual definition, and since it assumes a different function in tonal harmony, modal harmony, and chromatic harmony, its designation is also different.
In modal harmony, the tonal center is defined more precisely with the term: “CENTRAL MODAL ELEMENT”.
“Tonality” in tonal harmony and the “central modal element” in modal harmony have in common the fact that they remain constant throughout the duration of the piece. In other words, if in a tonal piece the tonality is, for example, D maj, it is preserved for the entire duration of the piece. Obviously, modulating islands, turnovers, cyclic structures like Coltrane changes, anatole, or convergent sequential structures may appear, but evaluated as a whole, the tonality remains the same.
In the same way, in modal harmony, the “central modal element” is the same throughout the duration of the piece. In modal harmony, the laws that determine chord sequences (contour) are different from the laws that determine chord sequences in tonal harmony; this is not the appropriate place to discuss this topic. I will provide an example of a modal chord sequence: D Aeolian-B Phrygian-Ab Locrian-F Dorian-D Aeolian-Bb Dorian-Gb Mixolydian-D Aeolian.
As you can see, D Aeolian is the central modal element that manages the modal movements rotating around it; the gravitation leading towards D Aeolian and the centrifugal force moving away from D Aeolian are functions of the tension degree of the individual modal scales. In contemporary modal harmony, the sequence of modes is established based on their tension degree. Less tense to more tense—more tense to less tense. In the past, the transition from one mode to another was based primarily on the typical notes of the mode; for example, the typical note of C Lydian is F#, and the typical note of F Phrygian is also F#. By using this note, it is possible to move easily and flexibly from C Lydian mode to F Phrygian mode and vice versa.
The concept of "Tonality" is therefore profoundly different from the concept of "Central modal element" because in modal harmony we also move away significantly from what might be considered the base tonality only to return to it when we wish, and we choose the modal harmonic progressions ourselves; instead, in tonal harmony, we do not have all this freedom, as we are constrained by the tonal hierarchy to repeatedly use always the same harmonic progressions.