Minor 9th

Notes and formula

The formula is 1 – ♭3 – 5 – ♭7 – 9, or 0 – 3 – 7 – 10 – 14 in semitones. A minor seventh chord with the second degree added an octave up.

The ninth here is a major ninth even though the chord is minor, and that combination is what gives it its particular sweetness. Flatten it and the chord becomes something else entirely — a minor seventh with a flat ninth is a harsh, rarely used sound, whereas the natural ninth is one of the smoothest additions in harmony.

How to play it

On piano the practical voicing puts C in the left hand and E♭–G–B♭–D in the right, or drops the fifth entirely: C in the bass, E♭–B♭–D above. As always, the third and seventh define the chord and the fifth is optional.

On guitar the common form is x3133x, sounding C–E♭–B♭–D. It is a movable shape with the root on the fifth string, and it is the shape most players learn before any other extended chord because nothing in it requires a full barre.

What it does in a progression

A minor ninth fills the same slot as a plain minor seventh — the ii of a ii–V–I, or a tonic in a modal piece — and does so with more colour and no added instability. Substituting Dm9 for Dm7 in a standard is safe by default; the reverse is what an arranger does when the texture is getting crowded.

As a tonic it is the defining sound of neo-soul and of a great deal of house and downtempo. A Cm9 held for four bars sounds like a decision rather than a wait, which a plain Cm7 does not quite manage.

Voicing it so the ninth is heard

The chord only works if the ninth has room. D placed directly above C sounds like a mistake; the same D an octave higher sounds like the reason the chord was chosen. Keeping the two at least a ninth apart is the single rule worth following.

On guitar this happens automatically, because the shape spreads across strings. On piano it does not, which is why the same chord that sounds rich under one player's hands sounds thick under another's.

Minor ninth or minor sixth-ninth

Both are five-note minor chords with a ninth, and they differ in the note above the fifth. Cm9 has a B♭, a minor seventh. Cm6/9 has an A, a major sixth, and no seventh at all.

The sixth version sounds brighter and more final, which is why it is the traditional last chord of a minor-key jazz arrangement; the ninth version sounds open and unfinished, which is why it is the one that loops.

Scales that contain it

Dorian and Aeolian both fit, and once again the difference is the sixth degree. Dorian is the more common choice over a minor ninth because the raised sixth matches the chord's brightness; Aeolian makes the same chord sound more mournful without contradicting a note of it.

Phrygian does not fit. Its lowered second is the ninth of the chord flattened, so it clashes with the D that defines the sound — one of the few cases where a mode that suits the underlying seventh chord fails on the extended one.

Frequently asked questions