Compositional Techniques
Review on Modal Cadences
Each mode has their own set of cadences. The chords in their cadences will contain the accidental that is character to the mode and the tonal center of that respective mode. It is important to have knowledge of the modes' accidentals and some common modal cadences before advancing further.
Dorian Mode
Accidental: M6
Cadences: viº, i
IV, i
ii, i
Accidental: M6
Cadences: viº, i
IV, i
ii, i
Phrygian Mode
Accidental: m2
Cadences: II, i
vii, i
vº, i
Accidental: m2
Cadences: II, i
vii, i
vº, i
Lydian Mode
Accidental: A4
Cadences: ivº, I
II, I
vii, I
Accidental: A4
Cadences: ivº, I
II, I
vii, I
Mixolydian Mode
Accidental: m7
Cadences: VII, I
v, I
iiiº, I
Accidental: m7
Cadences: VII, I
v, I
iiiº, I
*Locrian Mode contains two accidentals, m2 and d5, and is very different from the other modes. The most common cadence used is a bV, iº.
Review on Modulation
A modulation is a shift in tonal center, either by common chord modulation or chromatic modulation. In a common chord modulation, the pivot chord is diatonic in both the old key and new key. In a chromatic modulation, the pivot chord—when it exists in a piece—is either diatonic to only one key or neither key. A common way to chromatically modulate is to use a secondary dominant or leading tone chord because it emphasizes the new tonal center.
Why do the secondary dominant and leading tone chords pull to the new key so strongly? One could come up with a plethora of reasons, but perhaps the simplest answer is that we are used to the sound from years of listening. However, I believe it is a bit further than that and it is fair to say we are used to listening to the Ionian mode, the common major scale; therefore, it is important to look at the characteristics of Ionian mode that separate it from the other major modes.
Ionian Mode
Ionian mode is different from Lydian such that Lydian has a raised fourth, and Ionian is different from Mixolydian such that Mixolydian has a lowered seventh. Therefore, the interval between the fourth in the fifth in Lydian and Mixolydian is a perfect fourth, while in Ionian it is a tri-tone. This does not seem significant until we notice that the tri-tone exists in the dominant seventh chord and the leading tone chord.
Why is this important? The reason I bring up this point is that I believe that the majority of modulations we hear are based off of the Ionian mode. This is evidenced by the secondary dominant and leading tone chords that are used so often. Instead of using those chords, we could use modal cadences to change tonal center.
Combining the Concepts
Here is a piece I composed that illustrates the idea of modal modulation such that there are no secondary dominants or leading tones used, yet we are pulled to a new key. Both the old and new keys are in the Phrygian mode.
| red_slumber.pdf |
Related Keys
While theoretically it is possible to modulate to any key, a good place to start would be knowing the related keys. The related keys are notes within the scale—excluding the scale degree that is the root of a diminished chord. For example, if we have a C phrygian scale, our related keys would be Db, Eb, Fm, Ab, and Bbm. In general, the same concepts used in modulating with ionian, aeolian, and harmonic minor are used with the rest of the modes.
