Abmadd9 is Ab, Cb, Eb and Bb — Abm 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.

| Ab | Cb | Eb | Bb |
|---|---|---|---|
| 1 | ♭3 | 5 | 9 |
Minor tonic — a triad with one colour on it.
Also written Abm(add9), Abmin(add9) or Ab-add9. The same chord either way; which spelling you meet depends on who wrote the chart.
The same operation one voice further down: the third voice from the top falls an octave and becomes the bass.
That leaves a bigger hole under the top three notes, so a string gets skipped: the muted string in the middle is the shape, not a mistake.
Abmadd9 has 8 of them, on strings 6-4-3-2 and strings 5-3-2-1, from open position up to the 11th — every inversion the chord has: Ab in the bass, Cb in the bass, Eb in the bass and Bb in the bass. The one to learn first is the Ab shape at the nut.
4 of them sit on strings 6-4-3-2, so you can run the inversions up one set without changing strings — which is the whole reason to learn them as a family rather than as separate grips.
Start with 42x34x — no barre and down at the nut. None of the shapes for Abmadd9 uses an open string, so every one of them is movable; the lowest sits at the 2nd fret. 2 of the 7 need a barre. Together they cover the neck from the 2nd fret to the 14th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| 42x34x | 2nd fret | Ab, root position | Eb | all fretted |
| 466446 | 4th fret | Ab, root position | Bb | barred |
| xx6446 | 4th fret | Ab, root position | Bb | all fretted |
| xx9896 | 6th fret | Cb, 1st inversion | Bb | all fretted |
| x-11-9-8-11-x | 8th fret | Ab, root position | Bb | all fretted |
| x-11-9-x-11-11 | 9th fret | Ab, root position | Eb | barred |
| x-14-13-13-11-x | 11th fret | Cb, 1st inversion | Bb | all fretted |
The same notes rebuilt from scratch give 13 drop 2 voicings, each on its own page.
How you get to it. The turn that lands on Abmadd9 is Bbm7♭5 to Eb7♭9: the ii and the V of Ab minor, which is where a minor tonic is usually arrived at rather than simply begun on.
In which keys. Every note of Abmadd9 belongs to Eb minor (the iv, the subdominant), F# major (the ii, the supertonic), Ab minor (the i, the tonic) and B major (the vi, the submediant).
Every note of Abmadd9 is in Ab dorian, Ab natural minor, Ab harmonic minor and Ab melodic minor.
Change one note of Abmadd9 and you have Abm (drop the ninth), Absus2 (drop the minor third), Abm6 (the ninth becomes a sixth), Abm69 (add the sixth), Abm7 (the ninth becomes a flat seventh) or Abm9 (add the flat seventh).
Abmadd9 is a minor chord — root, minor third, fifth. Minor chords on every root.
On Abmadd9’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.