Root, third and seventh: the guide tones fix the quality, so the fifth is dropped. That is what leaves a string free, so pick a tension to put on top.
Ab7sus4 is Ab, Db, Eb and Gb — Ab7 with the third replaced by the fourth.
It sounds leaning rather than shoving. It keeps the flat seventh’s pull and loses the tritone, so it moves without making a hard cadence.

| Ab | Db | Eb | Gb |
|---|---|---|---|
| 1 | 4 | 5 | ♭7 |
Dominant — it points a fifth down, but softly.
Also written Ab7sus or Ab dominant 7 sus 4. The same chord either way; which spelling you meet depends on who wrote the chart.
Root, third and seventh. The third and seventh, the guide tones, are what make the chord major, minor or dominant, so the fifth can go: it says nothing the symbol needs.
Three notes means a spare string, which is the real point. Put a tension on it.
Ab7sus4 has 5 of them, on the bottom three strings, the low-middle three, strings 6-4-3 and strings 5-3-2, from the 4th fret up to the 11th — all in one inversion, so the bass note never moves. The one to learn first is the Ab shape at the 4th fret, which is the easiest grip here.
Start with xxx122 — no barre and only 3 fretted notes. None of the shapes for Ab7sus4 uses an open string, so every one of them is movable; the lowest sits at the 1st fret. 3 of the 7 need a barre. Together they cover the neck from the 1st fret to the 14th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| xxx122 | 1st fret | Ab, root position | Gb | all fretted |
| xx1122 | 1st fret | Eb, 2nd inversion | Gb | all fretted |
| 464644 | 4th fret | Ab, root position | Ab | barred |
| xx6879 | 6th fret | Ab, root position | Db | all fretted |
| x-11-11-11-9-9 | 9th fret | Ab, root position | Db | barred |
| x-11-13-11-14-11 | 11th fret | Ab, root position | Eb | barred |
| x-x-13-13-14-14 | 13th fret | Eb, 2nd inversion | Gb | all fretted |
The same notes rebuilt from scratch give 13 drop 2 and 9 drop 3 voicings, each on its own page.
Tensions. A shell of Ab7sus4, root, third and seventh, leaves a string free, and the tones that belong over it are the 9 (Bb) and the 13 (F).
In which keys. Every note of Ab7sus4 belongs to C# major (the V), C# minor (the v), Eb minor (the iv), E major (the iii), F# major (the ii), Ab minor (the i), Bb minor (the ♭VII) and B major (the vi).
Every note of Ab7sus4 is in Ab minor pentatonic, Ab blues, Ab mixolydian, Ab dorian and Ab natural minor.
Change one note of Ab7sus4 and you have Absus4 (drop the flat seventh), Abm7 (the fourth becomes a minor third), Ab7 (the fourth becomes a major third) or Ab11 (add the ninth).
Ab7sus4 is a suspended chord — root and fifth, with a second or fourth where the third would be — or nothing at all. Suspended and power chords on every root.
On Ab7sus4’s sound and use this page follows Mark Levine, The Jazz Theory Book (Sher Music, 1995). 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.