Chord sequence
Bm7 E7 Cm7 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 Bb major
Chords 1 to 2
Bm7 E7
Chords 3 to 4
Cm7 F7
Over Bm7 · ♭ii7
Mode 6 of Blues
Over E7 · V7/vii
Over Cm7 · ii7
Mode 2 of Major
Over F7 · V7
Mode 5 of Major