F♭ Phrygian — Quartal voicings
Three-note stacks of fourths, one per scale degree — the open, ambiguous voicing-flavour McCoy Tyner and Bill Evans built modal-era jazz around (the 'So What' chord).
All 7 quartal voicings in sequence
Degree 1 · I(4)Fb(4)
Degree 2 · Degree 2G𝄫·C♭·F♭
Degree 3 · III(4)Abb(4)
Degree 4 · IV(4)Bbb(4)
Degree 5 · V(4)Cb(4)
Degree 6 · Degree 6D𝄫·G𝄫·C♭
Degree 7 · VII(4)Ebb(4)