Chord substitution refers to the art of changing and/or adding chords to a progression in order to create harmony that is different and more interesting. “The general chord substitution rule holds that chords that share two or more notes in common can be readily substituted for each other” (Money Chords). Substitutions that share two or more notes in common are referred to as a common tone substitution. Any chord substitution must sound good and your ear is always the final arbiter of acceptability. The box below shows several examples of frequently used common tone substitutions. (Excerpt from Chord Progressions For Songwriters)

MoneyChords Lessons

Bass Line Movement - Part I

Backcycling - Part II

Chord Quality Change - Part III

Diminished Seventh Substitution - Part IV

Dominant Seventh Substitution - Part V

Embellishments - Part VI

Half-Step Substitution - Part VII

IIm-V Substitution - Part VIII

Inversions - Part IX

Mediant and Relative Major/Minor Substitution - Part X

Scalewise Substitution - Part XI

Tritone Substitution - Part XII

Chord Synonyms - Part XIII

Quartal Harmony - Part XIV

Other Lessons

A Chord Substitution Primer (MaximumMusician)

Chord Substitution Generator (Changes '98)

Reharmonization (MoneyChords)

Substitution Rules (WholeNote)