Chord sequence
B7 E7 A7 D7 D♭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 Db major
Over B7 · V7/♭III
Mode 4 of Melodic Minor
Over E7 · V7/♭VI
Over A7 · V7/♭II
Over D7 · subV7
Over Dbmaj7 · Imaj7
The major scale and its modes are the most commonly used scales in western music.