Audio: modal harmony (0:08)
modal harmony plays modal harmony on a fiddle accompanied by an acoustic guitar. The modal harmony figure shows the score and the table lists the chords to be found in each of the seven modes.
Modal harmony is rather a vague term. We use it to mean harmony that is written in a mode and is neither major harmony nor minor harmony.
Modal harmony is not major harmony. Major harmony uses a mode, the ionian, and the ionian is the same as the major scale. However, major harmony is a subset of functional harmony and modal harmony does not follow the rules of functional harmony. Similarly, modal harmony is not minor harmony. Although the natural minor scale is the aeolian mode and is occasionally used in minor harmony, neither the melodic minor scale nor the harmonic minor scale are modes.
The use of modes is a characteristic that pop harmony shares with jazz harmony and counterpoint. Modes are not used in functional harmony.
There are no new chords in modal harmony. The chords are the same as those in major harmony. Each mode contains three major triads, three minor triads and one diminished triad, as shown in the modal harmony table. Occasionally, you may come across a reference in the literature to a modal chord. Strictly speaking, there is no such thing. A modal chord is exactly the same as a chord in major harmony. This is because all the modes have the same notes as the ionian mode, the major scale, thus, the chords formed from these notes are the same in all seven modes.
Modal chord progressions sound different to major and minor harmony. Writing a modal chord progression is straightforward, the chords are the same as in major harmony, it is their order that is different. The beloved I-IV-V progression of major harmony becomes, for instance, the much less familiar, though no less beloved, I-IV-v in mixolydian or I-ivo-V in lydian.
Modal progressions in the mixolydian and lydian modes are a good alternative to major harmony. Lydian has a major tonic I triad, a major dominant V triad, and a leading note that is a semitone from the tonic. The difference is that the lydian has a diminished subdominant ivo not a major subdominant IV. The mixolydian has a major tonic I triad and a major subdominant IV triad. Its dominant triad is a minor v. Neither the mixolydian nor the lydian has the IV-V progression found in major harmony. In fact, the IV-V progression does not exist in any mode except the ionian, and the use of IV and V chords is diagnostic of major harmony. The nearest you will get to IV-V is IV-v in the dorian and mixolydian modes and iv-V in, surprisingly, the locrian.
Minor modal progressions, not uncommon in pop music, especially folk music, follow the same unusual pattern as their major counterparts. The i-iv-V progression, the cornerstone of minor harmony, does not exist in modal harmony. Instead, there is i-iv-v in aeolian harmony, i-IV-v in dorian, i-iv-vo in phrygian, and the weird sounding io-iv-V in locrian.
An interesting feature of the modes is that the leading note is a whole tone below the tonic, not a semitone, except in the lydian and ionian. In major and minor harmony the leading note is always a semitone below the tonic. That is where it got its name from, the leading note leads up by a semitone to the tonic. A leading note that is a whole tone below the tonic does not lead anywhere.
Modal chords can be voiced in different ways. A triad in modal harmony can be voiced in the same way as in major and minor harmony. A triad can also be incomplete. Importantly, the third can be omitted and the chord voiced in second inversion, both practices that are forbidden in functional harmony. All the guitar chords in modal harmony are incomplete, half are in second inversion, and only two chords contain the interval of a third. This approach to voicing accounts for the distinctive hollow sound of modal harmony.
Modal harmony marks a subtle but important change in the nature of harmony. The triad, top dog in functional and pop harmony, loses its preeminence. It continues to fight a rearguard action in modal and pentatonic harmony but loses it in quartal harmony and is displaced by the massive seventh chord with four different notes in jazz harmony. However, the sun shines but briefly on these new chords and they, too, disappear, along with the scales, and even the idea of key, in the primordial soup of chromatic and synthetic harmony. Life finds a way, as they say.