Chord sequence
F♯m7 D♯m7♭5 G♯m7♭5 C♯7alt
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 F# minor
All the chords
The I-vi-ii-V of a minor key: the minor i, a half-diminished vi and ii, and an altered V.
Over F#m7 · i7
Mode 2 of Major
Over D#m7b5 · viø7
Mode 7 of Major
Over G#m7b5 · iiø7
Over C#7alt · V7alt
Mode 7 of Melodic Minor