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.
Ab9#11 is Ab, C, Eb, Gb, Bb and D — Ab9 with the raised eleventh added on top.
It sounds wide and glassy, bright rather than tense. The ♯11 clears the major third by a whole step, so it adds height without the collision a natural eleventh makes.

| Ab | C | Eb | Gb | Bb | D |
|---|---|---|---|---|---|
| 1 | 3 | 5 | ♭7 | 9 | ♯11 |
Dominant — the lydian dominant sound.
Also written Ab9(#11), Ab9+11 or Ab9♯11. 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.
Ab9#11 has 8 of them, on the bottom four strings, the top four strings, the middle four strings, strings 6-4-3-2 and strings 5-3-2-1, from the 3rd fret up to the 10th — all in one inversion, so the bass note never moves. The one to learn first is the Ab shape at the 3rd fret, which is the easiest grip here.
Start with 4x453x — no barre and low, at the 3rd fret. None of the shapes for Ab9#11 uses an open string, so every one of them is movable; the lowest sits at the 3rd fret. 3 of the 6 need a barre. Together they cover the neck from the 3rd fret to the 13th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| 434334 | 3rd fret | Ab, root position | Ab | barred |
| 4x453x | 3rd fret | Ab, root position | D | all fretted |
| 454544 | 4th fret | Ab, root position | Ab | barred |
| xx6778 | 6th fret | Ab, root position | C | all fretted |
| x-11-10-11-11-10 | 10th fret | Ab, root position | D | barred |
| x-11-12-11-13-x | 11th fret | Ab, root position | C | all fretted |
The same notes rebuilt from scratch give 14 rootless and 1 open string voicings, each on its own page.
Tensions. A shell of Ab9#11, root, third and seventh, leaves a string free, and the tones that belong over it are the b13 (Fb) and the 13 (F).
Ab9#11 is a dominant with its tension raised, so it still points at Db — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.
Every note of Ab9#11 is in Ab lydian dominant.
Change one note of Ab9#11 and you have Ab9 (drop the flat fifth), Ab9b5 (drop the fifth) or Ab13 (the flat fifth becomes a sixth).
Ab9#11 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On Ab9#11’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.