Last year I came up with a new type of harmonic organization in music that I have named tetramodality. As the name suggests, it involves the blending of four modes, though of course this method could end up being trimodality or bimodality, as well. In other words, a generic term might be polymodality.
The inspiration for polymodality originally came from the technique of planing. For those who don’t know what planing is, it is a technique in which a series of harmonies are sounded such that they move in perfect parallel. In other words, Bach would kill a kitten if someone had proposed this technique to him. This technique was developed and mostly used during the Impressionism era of music by composers such as Claude Debussy. It is an absolutely gorgeous technique. It is used in one of my favorite piano solo pieces in existence: Debussy’s La cathédrale engloutie.
The above example is an example of diatonic planing, in which the parallel harmonies remain within the same key signature. This means that the chords can change between major and minor. There also exists chromatic planing, in which the chord’s quality is maintained, causing the chords to leave the key signature. In my opinion diatonic planing is generally much prettier.
Every once in a while, however, diatonic planing will have its own chromaticism. This usually happens when the composer wishes to avoid any diminished chords (i.e. with a root of scale degree seven in a major scale). In such cases, the composer might make it a B♭. This will only happen with that bottom voice, however.
In other words, one could technically make the argument that the above example is bimodal. The bottom voice is in C mixolydian while the other two voices are in C ionian (major scale).
Well, I found this incredibly interesting. I decided that it might be interesting to try other modes, and perhaps try putting other voices in a different mode, rather than, or in addition to, the bottom voice. This is from where the idea of polymodality came.
Originally it was the idea of trimodality. I would put each of the three voices in a different mode and see what I came up with. For example, we could try starting out with the hybrid mode of Phryggian-Dorian in the root voice.
In this example, let’s keep perfect fifths throughout so as to avoid any diminished chords (this is exactly what Debussy sometimes did). If we find a perfect fifth above every note in this scale, we end up with the C ionian-aeolian hybrid scale.
Next we need to determine what mode to use for the third of each chord. Whatever we choose, it cannot result in any thirds which would make the chord anything other than a major or minor chord. This rules out lydian, which would disrupt the II chord, lydian-mixolydian, which would disrupt the II chord, and lydian ♯5 which would disrupt the II and III chords. For this example, I’ll choose to use aeolian-ionian.
I could end here, and this is originally where I stopped. I started to use trimodality in compositions in planing situations, but then I expanded it into the general harmonies used throughout the composition. When I began using it, however, I started to add sevenths and was unsure what quality they should be. Therefore, I added a fourth mode to determine the sevenths of each chord. In this example, I want to keep minor-minor and major-major sevenths throughout so as to avoid dominant sevenths. Let’s choose lydian-mixolydian.
As you can see, this technique creates incredibly chromatic harmonies (in fact this particular tetramode yields all twelve chromatic pitches), and yet it is incredibly easy to avoid dissonance. This particular combination of four modes is precisely what I used in the middle section of my composition O Cool is the Valley Now (though it is in D, not in C). I used a different tetramode during the beginning and end of the piece. It looks as though it would sound very, very strange, but I was told by multiple people after its premiere that it was quite beautiful.
In this particular piece I avoided all non-perfect fifths and all dominant chords. This means that there was very, very little dissonance except what was created by the sevenths and by suspensions and other non-chord-tones. The next time I use polymodality, I plan to somehow involve more dissonance.