Chords in G Dorian

G Dorian is built from the notes G, A, Bb, C, D, E and F. Its scale carries 1 flat. Harmonising that scale in thirds gives seven chords — 3 majors, 3 minors and 1 diminished — starting on Gm as the i. The chord on the fifth degree is Dm rather than a major V, so G Dorian has no leading tone and resolves by step and colour instead of by dominant pull — the sound that separates it from a plain G major.

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