How to insert passing chords

How to insert passing chords

1. Before a minor 7th chord, we could insert a passing chord - a flat major 7th chord (maybe plus a dominant 7th note), e.g. before a vi7 chord, put a flat VI major7. Same to ii7, and iii7.
2. Before a major chord, we could put a passing chord - a flat diminished 7th chord, e.g. before a V chord, put a flat v dim7 chord. Same to I, and IV?