Chord sequence
Amaj7 B♭dim7 Bm7 E7
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 A major
All the chords
The I-VI-ii-V with a diminished 7th chord on #I in place of VI7, so the bass rises by half steps from I to ii.
Over Amaj7 · Imaj7
The major scale and its modes are the most commonly used scales in western music.
Over Bbdim7 · ♭ii°7
Mode 7 of Harmonic Minor
Over Bm7 · ii7
Mode 2 of Major
Over E7 · V7
Mode 5 of Major