Add 9
add9
0 - 4 - 7 - 14Major + major 9th (no 7th)
About Add 9
An add9 chord is a major triad with the ninth added and no seventh — in C that is C, E, G and D, written Cadd9. It is the most-played extended chord on acoustic guitar, and the reason is mechanical as much as musical: on a guitar in standard tuning the ninth is usually an open string away.
Notes and formula
The formula is 1 – 3 – 5 – 9, or 0 – 4 – 7 – 14 in semitones from the root. The ninth is the second degree raised an octave, and the octave is what makes it work: D directly above C rubs, D a ninth above C rings.
The absence of a seventh is what defines the chord. Add B to Cadd9 and it becomes Cmaj9, a jazz chord; leave it out and the same added note sounds like folk, worship or nineties rock.
How to play it
On guitar Cadd9 is x32030, and its usefulness comes from what surrounds it: the shape shares two fretted fingers with an open G at 320003, so alternating the two takes almost no movement. That fingering economy is why the pair turns up in so many acoustic songs.
On piano the chord is C–E–G with D above, and the rule is the same one that governs every ninth: keep the added note far from the root. A D pressed against the C in the left hand undoes the chord.
How it sounds
An added-ninth chord is a major chord with more air in it. Nothing has been made unstable — there is no seventh, no tritone, nothing pulling — but the plainness of the triad is gone, and a strummed add9 can be held for four bars without sounding empty.
Guitarists often use it in place of a plain major for exactly that reason, and listeners rarely register a chord change at all. The substitution is one of the few that is essentially free.
Where you hear it
Acoustic pop, worship music and Britpop all lean on it heavily; the open-position Cadd9 with an open G string ringing is one of the defining sounds of nineties guitar writing.
It also appears in film and ambient piano writing, where the ninth spread across two hands gives a major chord the sense of hanging in the air that a plain triad cannot.
Add9, major ninth and sus2
Three chords add a D to a C major triad. Cadd9 keeps the third and has no seventh. Cmaj9 keeps the third and adds the seventh. Csus2 removes the third and has no seventh at all.
The audible difference is easy to hear once named: sus2 is neutral, add9 is bright, maj9 is jazz. Reading them as variants of one chord is the most common mistake in charts that use the add family.
Scales that contain it
Ionian, Lydian and Mixolydian all fit, since the chord requires a major third, a perfect fifth and a natural ninth and says nothing about the fourth or the seventh.
The major pentatonic contains the whole chord, which is why melodies over it so often stay inside five notes — and why the chord sounds so settled: nothing in the usual melodic vocabulary can contradict it.
Frequently asked questions
What notes are in a Cadd9 chord?
C, E, G and D. The standard open guitar shape is x32030.
What is the difference between Cadd9 and Cmaj9?
The seventh. Cmaj9 contains B as well, which is what gives it a jazz colour. Cadd9 has only the triad and the ninth, and sounds like an acoustic guitar chord because that is mostly where it is used.
Can I play add9 instead of a plain major chord?
Usually, yes. The added ninth introduces no tension and no pull, so the substitution changes the texture rather than the harmony — unless the melody sits on the note a semitone away from the ninth.