Chord sequence
B♭m7♭5 A7 A♭maj7
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
Over Bbm7b5 · iiø7
Mode 2 of Harmonic Minor
Over A7 · subV7
Mode 4 of Melodic Minor
Over Abmaj7 · Imaj7
The major scale and its modes are the most commonly used scales in western music.