A style of voicing made popular by McCoy Tyner is based on the interval of the fourth. This type of voicing is used most often in modal music. To construct a quartal voicing, simply take any note in the scale associated with the chord, and add the note a fourth above, and a fourth above that. Use perfect fourths or augmented fourths depending on which note is in the scale. For instance, quartal voicings for Cm7 are “C F Bb”, “D G C”, “Eb A D” (note the augmented fourth), “F Bb Eb”, “G C F”, “A D G”, and “Bb Eb A”. This type of voicing seems to work especially well for minor chords (dorian mode), or dominant chords where a suspended or pentatonic sound is being used.
These voicings are even more ambiguous, in that a given three note quartal voicing can sound like a voicing for any number of different chords. There is nothing wrong with this. However, if you wish to reinforce the particular chord/scale you are playing, one way to do this is to move the voicing around the scale in parallel motion. If there are eight beats of a given chord, you may play one of these voicings for the first few beats, then move it up a step for a few more beats. The technique of alternating the voicing with the root in the bass, or the root and fifth, works well here, too. On a long Cm7 chord, for instance, you might play “C G” on the first beat, then play some quartal voicings in parallel motion for the duration of the chord.
As with the 3/7 voicings, these voicings are convenient left hand voicings on the piano or three or four string voicings on the guitar. They can also be made into two handed or five or six string voicings by stacking more fourths, fifths or octaves on top. For instance, the Cm7 chord can be voiced as “D G C” in the left hand and “F Bb Eb” in the right, or “Eb A D” in the left and “G C G” in the right. The tune “So What” from the album Kind Of Blue used voicings consisting of three fourths and a major third. On a Dm7 chord, the voicings used were “E A D G B” and “D G C F A”.