Chord sequence
Fm7 B♭7 G♭m7 C♭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 E major
Chords 1 to 2
Fm7 Bb7
Chords 3 to 4
Gbm7 Cb7
Over Fm7 · ♭ii7
Mode 6 of Blues
Over Bb7 · V7/vii
Over Gbm7 · ii7
Mode 2 of Major
Over Cb7 · V7
Mode 5 of Major