Chords in G Locrian

G Locrian is built from the notes G, Ab, Bb, C, Db, Eb and F. Its scale carries 4 flats. Harmonising that scale in thirds gives seven chords — 3 majors, 3 minors and 1 diminished — starting on Gdim as the iø. The chord on the fifth degree is Db, a major bV, so G Locrian has the leading tone that makes a Db-to-Gdim cadence sound final.

Beyond those seven, G Locrian commonly borrows G (I), Am (ii), Bm (iii), C (IV) and D (V) from the parallel major — the mixture chords that give a progression somewhere unexpected to go.