Chord sequence
D♯m7♭5 G♯7♭9 C♯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 C# major
All the chords
A minor ii-V resolving to a major I: the half-diminished ii and the dominant's b9 darken the approach, then the major tonic brightens it.
Over D#m7b5 · iiø7
Mode 2 of Harmonic Minor
Over G#7b9 · V7♭9
Mode 5 of Harmonic Minor
Over C#maj7 · Imaj7
The major scale and its modes are the most commonly used scales in western music.