Quartal (4 notes)
q4
0 - 5 - 10 - 15Stacked perfect 4ths (4 notes)
About Quartal (4 notes)
A four-note quartal chord is built from three stacked perfect fourths — in C that is C, F, B♭ and E♭. Adding a fourth to the three-note stack does not make it more stable; it makes it wider, and it is the size at which quartal harmony stops sounding like a fragment and starts sounding like a language.
Notes and formula
The formula is 0 – 5 – 10 – 15 in semitones: three perfect fourths, spanning an octave and a fourth.
The chord contains no third and no perfect fifth above the root, so it has neither quality nor anchor. It does, however, contain a minor seventh between the bottom two and a minor seventh between the top two — which is why it sounds full rather than thin.
Moving it in parallel
The characteristic use is to slide the whole shape up and down a scale without changing its interval structure. Because every voice moves by the same amount, the result is a texture rather than a progression.
That is the technique modal jazz pianists built a style on: harmony that changes colour without changing function, over a bass that does not move.
How to play it
On guitar it is x–3–3–3–4–x, sounding C–F–B♭–E♭. Three strings at one fret and one a fret higher — the one-fret offset is where the guitar's tuning stops being in fourths, at the second string.
On piano the four notes span an eleventh and are usually divided between hands, which is also how they are voiced in an arrangement.
What it substitutes for
Read from E♭, the notes are E♭–B♭–F–C, which over a C bass is close to a minor eleventh voicing. Quartal shapes and tertian extensions overlap constantly, and which name applies depends on the bass note.
This overlap is useful rather than confusing: a player who knows the quartal shape can supply extended harmony without thinking in stacked thirds at all.
Searching for it
As with its three-note relative, nobody searches for this chord by name. It is learned from recordings and from voicing books, not from a chord dictionary.
The page is here so the catalogue is complete and so a reader who encountered the shape has somewhere to land.
Frequently asked questions
What notes are in a four-note quartal chord on C?
C, F, B♭ and E♭ — three perfect fourths stacked. On guitar, x–3–3–3–4–x.
Why does the guitar shape have one finger out of line?
Because the guitar is tuned in fourths except between the third and second strings, where the interval is a major third. The offset corrects for it.
Is it the same as a minor eleventh chord?
It overlaps with one. Read over the right bass note the same four notes function as part of a minor eleventh; read on their own they are a quartal chord with no root.