Chord sequence
Em7 A7 Fm7 B♭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 Eb major
Chords 1 to 2
Em7 A7
Chords 3 to 4
Fm7 Bb7
Over Em7 · ♭ii7
Mode 6 of Blues
Over A7 · V7/vii
Over Fm7 · ii7
Mode 2 of Major
Over Bb7 · V7
Mode 5 of Major