This chord is played start on fret 4 Minor seventh chord with added 13th (6th). Most of the time the 5th is left out (3rd note). The 13th = 6th 13th is used when the chord is a 7th chord with added 6th 6th chords are not 7th chords with added 6th.
Scale structure: R-m3-5-m7-13
Note: Ab B Eb Gb F
Alternative names: Abminor13, Abmin13, Abm7/13, Abm7(add13), Ab-7(add13), Ab-7/13, Abmin7/13, Abmin7(add13), Abm7/6, Abm7(add6), Ab-7(add6), Ab-7/6, Abmin7/6, Abmin7(add6)
Importance: Rarely used