Quartal harmony or harmonic structures based on the interval of a fourth will give us more material in our never ending quest for new and fresh sounding harmony within the tonal system. In addition this harmony will also enable us to create movement within an unchanging or “static” harmony. Let’s say we are playing through a tune like “Footprints” or any number of other tunes where we encounter a single harmony for a long period of time and want to add some movement within this static harmony. What do we do? One of the most effective ways of accomplishing this is through the use of quartal harmony that will move in a step-wise fashion over a static root. Let’s look at two of the more common situations; a long stretch of a major 7th harmony and a long stretch of a minor 7th harmony.
I think we would all agree that in the case of a major 7th chord the color tones that can be added are the major sixth, major ninth and the augmented or sharp eleventh. Our complete major 7th chord with all added embellishment tones (using CMaj7 as an example) would then be:
C-E-G-B-D-F#-A
Placing these tones in step-wise order produces the C Lydian mode:
C-D-E-F#-G-A-B
In the case of a minor 7th chord the added color tones would be the major sixth, major ninth and eleventh. Our complete minor 7th chord with all added embellishment tones (using Am7 as an example) would then be:
A-C-E-G-B-D-F#
Placing these tones in step-wise order produces the A Dorian mode:
A-B-C-D-E-F#-G
Notice of course that these two modes are relative in that they use the same pitches.
Now all we need to do is construct the quartal harmonies generated by these two modes.
Begin with C and simply stack fourths above each note of the scale in ascending order. We will use four note voicings for the examples:
C-F#-B-E, D-G-C-F#, E-A-D-G, F#-B-E-A etc.
Since the C Lydian and A Dorian modes are relative the quartal structures are the same in both cases. This makes it convenient and easy to remember that you can use the same voicings as embellishments for either C major or A minor which we already know are relative.
Notice that many of these voicings contain augmented fourths which may take a little getting used to. I would suggest playing the voicings over a droning C and A to get acclimated to the new sounds. Then apply them to any tune where you have a couple of measures of the same harmony or wherever you feel movement is needed and let your ear be the judge as to the appropriateness of the chords. I think you will find them to be quite interesting. The pdf file below shows the voicings on two string sets with diagrams for ease of reading.