Chord sequence
Gm7 C7 A♭m7 D♭7
In every key
Four-note rootless voicings in their two forms, with the 3rd or the 7th on the bottom, played over the root.
Heard in Gb major
Chords 1 to 2
Gm7 C7
Chords 3 to 4
Abm7 Db7
Over Gm7 · ♭ii7
Mode 6 of Blues
Over C7 · V7/vii
Over Abm7 · ii7
Mode 2 of Major
Over Db7 · V7
Mode 5 of Major