Harmoni1959, the 30th Street studio in New York. Miles Davis counts off the tempo of So What. Paul Chambers's bass poses its question, two notes, and the piano answers. That little answering chord, that suspended "amen" Bill Evans plays, would become one of the most copied sounds in modern jazz. It is not a chord of thirds. It is a stack of fourths. Welcome to the world of quartal chords on the piano, the harmony that gave modal jazz its unmistakable flavor.
All of classical Western harmony rests on thirds. C-E-G, a stack of thirds, and you have a major chord. Fourths break that logic. They produce a sound the ear cannot file into a major or minor box. That is exactly what the pianists of the late 1950s were after, tired of the grammar of bebop.
What is a quartal chord on the piano?
A quartal chord, also called quartal harmony, is built by stacking intervals of a fourth rather than a third. Start on a C. Instead of adding the third (E) then the fifth (G), you go up a fourth to F, then another fourth to Bb. C-F-Bb. Three notes, two fourths. The chord has no third and no obvious tonal color. It floats.
That absence of a third is the heart of the matter. The third is the note that tells the ear "I am major" or "I am minor." Remove it and replace it with fourths, and the chord becomes ambiguous, open, suspended. It can belong to several keys at once. That ambiguity, a disaster for a classical composer, becomes a richness for a modal jazz player. It opens space instead of closing it.
We distinguish the perfect fourth (the C-F, five semitones) from the augmented fourth, the famous tritone (C-F#, six semitones). Classical quartal harmony stacks perfect fourths. When a tritone slips into the stack, the sonority tightens and moves toward the Lydian sound. The two often cross in modern playing.
How to build Bill Evans's So What chord
The So What chord is the most famous quartal voicing in jazz. It takes its name from the tune on Kind of Blue where Bill Evans plays it. Its recipe fits in one sentence: three perfect fourths stacked, then a major third on top. Five notes in all.
Let's build it on E. Start from the low E, go up fourth by fourth, cap it with a major third:
| Note (bottom to top) | Interval from the previous | Hand |
|---|---|---|
| E | root | Left hand |
| A | perfect fourth | Left hand |
| D | perfect fourth | Right hand |
| G | perfect fourth | Right hand |
| B | major third | Right hand |
In practice, you split the chord across both hands: E and A at the bottom in the left hand, D-G-B on top in the right. Analyzed in tonal theory, this E-A-D-G-B is an E minor eleventh (Em11) with its third played first. But hearing it as an "Em11" misses the point. Its true color comes from the quartal structure, not from its label.
On the So What recording, the tune is in D Dorian. So Bill Evans plays the same voicing transposed: D-G-C-F-A. Eight bars later, the piece modulates to Eb Dorian, and he simply moves the chord up a half step, without changing its shape. That is the magic of quartal voicings: a single hand shape, slid along the keyboard. Want the exact detail of Evans's voicing? The So What chord page on Wikipedia documents it note by note.
Why fourths sound modern and ambiguous
Two reasons, one acoustic and one historical.
On the level of sound, the fourth is a more "neutral" interval than the third. The third is saturated with meaning: it carried three centuries of tonal harmony, it sounds like a precise emotional color. The fourth tells no tonal story. Stacked, it creates an open consonance, almost medieval, the sound of Gregorian organum, which belongs to no key in particular. The modern ear hears it as fresh because it escapes the gravity of major and minor.
On the historical level, fourths arrive at just the right moment. By the end of the 1950s, bebop had pushed harmonic complexity to its maximum. Charlie Parker's changes move to a new chord on every beat. Miles Davis wanted the opposite: to slow the harmony down, let a single mode breathe for sixteen bars, give the soloists air. Modal jazz was born. And it needed chords that impose no direction, that do not pull toward a resolution. Fourths, precisely because they float, were the perfect tool. They paint a color instead of narrating a tension.
McCoy Tyner and the left-hand revolution
If Bill Evans signed the most famous voicing, it is McCoy Tyner who made fourths an identity. The pianist in John Coltrane's quartet between 1960 and 1965, Tyner slams stacks of fourths in the left hand with an unprecedented force and density. Listen to his composition Contemplation, a minor blues built on stacked fourths, or his playing on A Love Supreme. His left hand does no walking bass and no discreet comping. It hammers quartal chords that ring like bells.
Tyner's move is simple to describe, hard to match. In the left hand, he often slams a fifth in the bass (the root and its fifth) while the right hand stacks fourths above it for the improvisation. That cocktail of fifths on the bottom and fourths on top became the signature of post-Coltrane jazz piano. Chick Corea, Herbie Hancock, later Brad Mehldau and Robert Glasper all draw from it. The pianist and critic Ethan Iverson goes so far as to speak of a "Tyner revolution" to describe this shift from the third to the fourth as a harmonic building block.
Herbie Hancock, for his part, uses it in a more muted way. On Maiden Voyage or Dolphin Dance, his suspended voicings, those sus chords that never quite resolve, owe everything to quartal logic. Where Tyner strikes, Hancock caresses. Same material, two temperaments.
Watch the fourths stack up on the keyboard
HarmoniKeys shows the structure of your chords in real time, fourths included, and shows you how to slide a hand shape from one degree to the next without distorting it. The best way to internalize the So What chord.
Open HarmoniKeysHow to play quartal chords on a modal tune
Theory is worth nothing until the fingers have played it. Here is a concrete practice plan on a modal chart, slow tempo, no pressure.
Step 1. The basic shape. Set up the So What chord on D (D-G-C-F-A), both hands. Play it, listen to it, let it ring. Do it again on Eb a half step higher. Then on F, on G. The same hand sliding. Do not try to improvise yet, just learn to feel the shape move.
Step 2. One mode, one chord. Take the beginning of So What or of Coltrane's Impressions, harmonically identical: sixteen bars of D Dorian, eight of Eb Dorian, eight of D Dorian again. Comp your quartal voicing over each section. You only have one chord to move up a half step and bring back. Dead simple, and yet it already sounds pro.
Step 3. Fourths in the melody. In the right hand, improvise going up in fourths rather than scales. D-G-C, a quartal fragment, then E-A-D, shifted. This movement in fourths within the improvisation is the second half of the modern sound. The D Dorian scale stays your reservoir of notes, but you travel it in fourth-leaps instead of stepwise degrees.
Step 4. Mix it up. Alternate quartal comping in the left hand and quartal fragments in the right. Twenty minutes a day for two weeks, and the McCoy Tyner sound starts coming out of your hands. Not in one evening. But it comes.
One last piece of advice. Fourths do not suit everything. On a fast tonal cadence, a ii-V-I that has to resolve cleanly, the third steers the ear better and asserts the function of each chord. Keep the fourths for the moments when the harmony slows, when a mode settles in and breathes. Used everywhere, they dilute everything into a blur. Used in the right place, they open a window.
To tie it all together, go see how modal improvisation leans on Kind of Blue, then compare with the logic of Bill Evans's rootless voicings, which pose the opposite question: what do you do when you keep the third but drop the root? Between the two, you hold almost the whole grammar of modern jazz piano. Happy practicing.