Chord substitutions add harmonic diversity.

Jazz Reharmonization

Reharmonize with alternate chord
of same function.

Chord	Family	Function
I	tonic family	temporary/permanent resting chord
IImi	subdominant family in major keys	move away from tonic
II^o	subdominant family in minor keys first inversion ^bVII triad often replaces II^o	move away from tonic
^bIII	tonic family in minor keys	temporary/permanent resting chord
IIImi	tonic family in major keys	temporary/permanent resting chord
IVmi	subdominant family in minor keys	move away from tonic
IV	subdominant family in major keys	move away from tonic
Vmi	dominant family in minor keys	move towards tonic or move towards new progression
V	dominant family in major keys also in raised 7th minor keys	move towards tonic or move towards new progression
^bVI	tonic family in minor keys	temporary/permanent resting chord
VImi	tonic family in major keys	temporary/permanent resting chord
^bVII	dominant family in minor keys	move towards tonic or move towards new progression
VII^o	dominant family in major keys also in raised 7th minor keys first inversion V triad often replaces VII^o	move towards tonic or move towards new progression