Abm6 is Ab, Cb, Eb and F — Abm with a major sixth added on top.
It sounds bittersweet — minor underneath, major on top. The major sixth over a minor triad comes from the melodic minor, and it is the classic jazz minor tonic.
Minor tonic — an ending chord in a minor key.

| Ab | Cb | Eb | F |
|---|---|---|---|
| 1 | ♭3 | 5 | 6 |
Also written Abmin6, Ab-6 or Ab minor 6. The same chord either way; which spelling you meet depends on who wrote the chart.
Abm6 in 1st inversion puts Cb in the bass instead of Ab, the 3rd of the chord. The notes are the same; what changes is what the bass line does, which is most of why you would reach for it — it lets the lowest voice move by step where the root would have jumped.
One of Abm6’s 8 common shapes does this:x2314x
Play Abm6 as a shell — root, third and seventh — and the spare string takes the 9 (Bb) or the 11 (Db).
All 8 common shapes as fret numbers, lowest string first. Hover or tap one to see it drawn.
How you get to it. The turn that lands on Abm6 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 Abm6 belongs to Eb minor (the iv, the subdominant) and F# major (the ii, the supertonic).
Every note of Abm6 is in Ab dorian, Ab melodic minor and Ab half-whole diminished.
Change one note of Abm6 and you have Abm (drop the sixth), Abdim7 (the fifth becomes the flat fifth), Abm69 (add the ninth), Abm7 (the sixth becomes the flat seventh), AbmMaj7 (the sixth becomes the major seventh) or Abmadd9 (the sixth becomes the ninth).
Abm6 is a minor chord — root, minor third, fifth. Minor chords on every root.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.