12 rules of French modal harmonization with triads

Yesterday I shared with you the harmonization of Gregorian chant sequence Dies irae in four parts. What was unusual with this exercise is that the chords were in the style of 20th century French modal organ composers. If you haven't seen the score, here are the PDF and MIDI files.

After this post a few people asked me to describe the rules of this type of harmonization so that they could learn to harmonize like that themselves. So today I decided to go into greater detail of how I do it.

1. Use three note major and minor chords only (such as C-E-G or A-C-E).
2. In four-part setting, double the root of the chord (in C major chord, double the note C).
3. When the melody descends, use closed position of the chords, when the melody ascends - open position.
4. Whenever possible, avoid parallel movement in all parts within the sentence - use as much contrary motion in the bass.
5. At least one voice has to be stationary or go to the opposite direction that others.
6. Avoid perfect 4th and 5th relationship in the chords because this will sound like in traditional classical tonal harmony (T-D, D-T, T-S, S-T). One possible exception of this rule might be at the very ending of the piece, but even then it's probably better to find other options. In my example, the last two chords are B minor and E minor. Now when I'm thinking about it, I would change B minor chord to D major. At any rate, minor-minor chords at the end are better than major-major because this eliminates D-T feeling.
7. Instead use major and minor third relationship between two chords up or down (such as C major - Eb major).
8. Major and minor second relationship up or down is also good (such as C major - Db major).
9. A tritone relationship sounds wonderful (such as C major - F# major).
10. If you have no other choice and have to use perfect 4th and 5th relationship between two chords, let one chord be major and another minor or vice versa (such as C major - F minor.
11. It is OK to use one major and one minor chord and vice versa, if they are not closely related (not only in instances, like in No. 10).
12. In general, the wider the distance of the two chords or keys within the circle of fifths, the better.

Apply these rules (in writing and/or in improvisation, because you can learn to do it spontaneously on the spot) on any hymn tune you want - chant, chorales, hymns, folk songs, even the National Anthem of your country. I'm sure your listeners will have something to talk about.

P.S. We only used major and minor triads in root position and the result is pretty colorful, I think. Imagine, what would happen, if we chose their inversions or diminished and augmented chords as well as seventh-chords and ninth-chords and their inversions? The color range would skyrocket in such case. That's what all these 20th century French master organists and composers did.

You can do it, too.