Ultimate Guitar Lesson

XI. Chord Families and Diatonic Substitution

Progressions strongly tend to move from the tonic family to the subdominant family, then to the dominant family, and then back to the tonic family.

Tonic Family
I iii vi

Subdominant Family
ii IV vi

Dominant Family
V vii

The vi chord may function as either tonic or subdominant depending on its place in the progression. In minor keys the bVI chord is always in the subdominant family.

Chords in the same family may be substituted for each other for variety. In the example below, a Dm chord may be used in place of F major in bar 2.
C | F |G | C |

Substitutes may be played in addition to the basic harmony to increase the sense of movement.

C Am |F Dm |G Bm7b5 |C |