Chords in Bb Phrygian

Bb Phrygian is built from the notes Bb, Cb, Db, Eb, F, Gb and Ab. Its scale carries 6 flats. Harmonising that scale in thirds gives seven chords — 3 majors, 3 minors and 1 diminished — starting on Bbm as the i. The chord on the fifth degree is Fdim rather than a major VØ, so Bb Phrygian has no leading tone and resolves by step and colour instead of by dominant pull — the sound that separates it from a plain Bb major.

Beyond those seven, Bb Phrygian commonly borrows Bb (I), Cm (ii), Dm (iii), Eb (IV) and F (V) from the parallel major — the mixture chords that give a progression somewhere unexpected to go.