Modal Harmony, Part II

(con't from Part I)
Ancient church modes were declamatory melodies, sang in unison, which phrases ended with fixed melodic and rhythmic formulas, thus had no cadence as we understand them with our 21st century essentially-tonal ears and minds.
The first real cadences, or clausules, appeared with the gradual development of polyphony, a turning point in Western music which began during the 10th-12th centuries, although we have no clear idea exactly how or when this type of music developed.
These cadences were the proximate cause for the disappearance of modes.
Modal harmonic cadences can be traced back to the 19th century when composers made various attempts to destruct tonality; but tonal culture is so deep-rooted in our minds that we want to make modal music a kind of tonal music transcription, especially due to functional harmony.
It's important to understand that modal cadences are NOT conclusive to the ear as would be tonal cadences and are generally used just to add a transitory color to a musical phrase.
The essential differences between tonal and modal harmony is a deep question, but in these postings we'll try to wade in from the shallow end and provide an answer that's clear:
Early modal music was primarily concerned with the horizontal or melodic aspects of music ... the counterpoint of moving lines, in other words, which preceded chordal harmony ... whereas tonal chord progressions did not come along until later.
The basic principle is very simple: chords are usually built using tones from the current scale, so we just lay them out as they come; if that scale is not major or harmonic minor, then we could say that we've got modal harmony.
Modal harmony, then, is that which uses chords that are built from only the tones available in one of the modes (photo).
Modal harmony is a totally different thing from the "functional" harmony used in major and minor keys.
What we want in modal harmony is chords that don't sound like they want to "lead" anywhere and not create the kind of tension between chords that we have in traditional functional harmony.
One answer is to use quartal harmony where chords are built by stacking 4ths instead of tertian 3rds; this creates ambiguous harmonies, which is exactly what some composers like Debussy and Ravel wanted.
Because our chord language is based on the tertian system, this creates what we call "sus" chords, even though they don't behave as suspensions are conventionally supposed to.
A classical suspension is a tension that has to resolve; a modal chord has no such tendency.
The way many jazz players stop these "sus" chords sounding like they need to resolve is mainly by doggedly NOT resolving them; this creates a kind of static, open-ended feel.
In place of the often frantic roller-coaster of chord progression in keys, modal harmony provides something peaceful ... a single mood.
We find that the major key (Ionian mode) is such a powerful force, that if we use too many chords in it, the whole thing is going to start gravitating towards the major key; thus in some modal pieces we find just one chord with perhaps 1 or 2 other secondary, contrasting chords, to deliberately keep the music vague.
For example, while Lydian is a very stable mode, acoustically it's quite a weak one; that tritone between the root and sharp 4th is always threatening to want to resolve inward or outward to the two semitones adjacent, and if we want to stay in Lydian, we can't let it do that (we can, of course, leave the sharp 4th out of the chord and just use it melodically).
Modes cannot be "applied" within keys through an entire composition as it would make no sense to do so, although a short modal passage inserted in a tonal piece can impart an interesting effect; combining "relative modes" (e.g., using F Lydian in the key of C Major) would make no sense either, because it's pretty much just the same notes ... actually, it's the CHORDS (especially their arrangement in a progression) which govern the modal sound(s), not any specific pattern of those 7 scale notes that we might choose.
Musicians sometimes experiment with modes to evoke a certain mood, and they do it almost intuitively without really knowing why, just recognizing something in that scale that spoke to them, that they wanted to use.
Such experiments have been going on for centuries, all the way through the classical obsession with major and minor keys (a very narrow but fertile application of 2 particular modes, Ionian and Aeolian) right up through the present day.
Therefore, in a way, we have modes in our blood, our genes, our subconscious; when we hear them, they sound natural in some way, slightly strange, but also deeply familiar.
The major scale (and the whole European system of "keys") is a historical anomaly in the story of world music; in a sense, it's like a hothoused plant -- one particular mode, bred in captivity, forced into flowering into the amazing abundant display of classical music, which bloomed phenomenally and productively for 200-300 years (a tiny blip in human history).
Ionian mode was the seed, and the concept of tertian harmony (stacking chords in 3rds, basically) was the fertilizer.
In other words, there is a lot that is artificial -- not natural -- about the key system, believe it or not.
Equal temperment, which is necessary to enable us to modulate between keys at will (without retuning) is an awkward compromise -- a "genetic modification" of Ionian, if you like [See blog, Temperaments and Tuning, Parts I-V].
This centuries old obsession of the West with harmony and tonality has mostly deafened us to the qualities of other kinds of music; we're in the habit of describing other kinds of music as "primitive" just because it doesn't use chords.
We're so wedded to the notion that harmony is the king, the sole criterion of sophistication and artistry in music, that (traditionally at least) we still feel Beethoven (et al) is superior to anything the rest of the world can produce.
Naturally we are only being loyal to our own cultural history, and there's nothing wrong with that.
Everyone feels that the kind of music they grew up with is "natural" - and it is, to them.
The organ scholar might wonder how a piece of music in a mode such as Lydian or Mixolydian is supposed to sound so different from the progressions of what they and the rest of civilized society are already used to when their differences are literally as minimal as Western music allows ... only 1 scale alteration, and only a half step to boot!
Of course, they'd be right in that modal differences are not huge, but, then again, nobody is really saying they are (there's a lot of mythology attached to modes); and yet, it has ramifications for how the harmony is organized (what kind of chords we can string together); that's where the differences between "keys" and "modes" start to have real impact.
If we're actually listening and not just contemplating differences "on paper," that one note alteration actually makes all the difference, and that's the whole point; when we think about it, 1 note in 7 is quite a high proportion of the material.
As for "only a half step," we can try looking at the difference between any parallel major and minor chords, such as C Major and c minor, to convince us that the mere difference of a half step can have tremendous effect; if someone thinks only a half step is a trivial difference, then it can be strongly argued that they're not really listening.
(con't in Part III)