Chord sequence
B♭m7 E♭7 A♭maj7 F7
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 Ab major
Chords 1 to 3
Bbm7 Eb7 Abmaj7
Over Bbm7 · ii7
Mode 2 of Major
Over Eb7 · V7
Mode 5 of Major
Over Abmaj7 · Imaj7
The major scale and its modes are the most commonly used scales in western music.
Over F7 · V7/ii
Mode 5 of Melodic Minor