An open string left ringing against a fretted grip. Because it costs no finger, it sounds a note the closed shape has none left for -- a tension on top, or a pedal root underneath. Either a familiar grip with open strings added, or a shape so sparse the open strings carry the chord. These belong to their key rather than to a shape, so D, A, G and E have many and Eb a handful.
Cmadd9 is C, Eb, G and D — Cm with the ninth added, and no seventh.
It sounds sharp-edged. The ninth grinding a whole step under the minor third is the edge an m9 softens.

| C | Eb | G | D |
|---|---|---|---|
| 1 | ♭3 | 5 | 9 |
Minor tonic — a triad with one colour on it.
Also written Cm(add9), Cmin(add9) or C-add9. The same chord either way; which spelling you meet depends on who wrote the chart.
An open string left ringing against a fretted grip. It costs no finger, so it can sound a note the closed shape has none left for: a tension on top, or a pedal root underneath.
These belong to their key rather than to a shape: they cannot be moved up the neck. D, A, G and E have many; E♭ has a handful.
Cmadd9 has 3 of them, on the top four strings, strings 6-4-3-2 and the bottom four strings, all of them at the 3rd fret — every inversion the chord has: G in the bass and D in the bass. The one to learn first is the D shape at the 3rd fret, which is the easiest grip here.
Start with x30543 — no barre and 1 open string. 2 of the 8 shapes here sit in open position. 3 of the 8 need a barre. Together they cover the neck from the 1st fret to the 15th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x31033 | open position | C, root position | G | barred |
| x30543 | open position | C, root position | G | 1 open string |
| x6553x | 3rd fret | Eb, 1st inversion | D | all fretted |
| 860788 | 6th fret | C, root position | C | barred |
| 8-10-10-8-8-10 | 8th fret | C, root position | D | barred |
| x-x-10-8-8-10 | 8th fret | C, root position | D | all fretted |
| x-x-13-12-13-10 | 10th fret | Eb, 1st inversion | D | all fretted |
| x-15-13-12-15-x | 12th fret | C, root position | D | all fretted |
The same notes rebuilt from scratch give 13 drop 2 and 8 drop 3 voicings, each on its own page.
How you get to it. The turn that lands on Cmadd9 is Dm7♭5 to G7♭9: the ii and the V of C minor, which is where a minor tonic is usually arrived at rather than simply begun on.
In which keys. Every note of Cmadd9 belongs to C minor (the i, the tonic), Eb major (the vi, the submediant), G minor (the iv, the subdominant) and Bb major (the ii, the supertonic).
Every note of Cmadd9 is in C dorian, C natural minor, C harmonic minor and C melodic minor.
Change one note of Cmadd9 and you have Cm (drop the ninth), Csus2 (drop the minor third), Csus2sus4 (the minor third becomes a fourth), Cm6 (the ninth becomes a sixth), Cm69 (add the sixth) or Cm7 (the ninth becomes a flat seventh).
Cmadd9 is a minor chord — root, minor third, fifth. Minor chords on every root.
On Cmadd9’s sound and use this page follows Robert Rawlins & Nor Eddine Bahha, Jazzology (Hal Leonard, 2005). The shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.