Triadic Chord Families

The diatonic chords in a given key share certain pitches and characteristics which allow them to be grouped into families.  These chord families capitalize on the hierarchy of melodic stability of the individual pitches in a key to create different effects in a chord progession.  Understanding these families is helpful in creating motion in your chord progressions and substituting chords for one another.  

Tonic Family

As the I chord is the tonic of the key, the pitches in the I chord are regarded as the most stable.  Likewise, chords that share more than one pitch with the I chord also create a sense of stability.  In any major key, these chord will be the I, III minor and VI minor.   By looking at the table below we can see what chords fall into the Tonic Family in the key of C and the notes which they share.  Notes in bold are shared with the I chord.

Since the I chord is often referred to as feeling like “home”, chords in the tonic family are used to create varying degrees of stability in chord progessions.  Generally, the VI minor chord sounds more stable than the III minor chord due to the latter’s inclusion of the unstable leading tone (a topic we will discuss in the Dominant Family section and denoted in the table above with an asterisk).  Any of the chords in the Tonic Family can be substituted for one another and are often used to create deceiving notions of “home”.  They are frequently used to start and end a section.

Subdominant Family

The fourth scale degree of the major scale is referred to as the “characteristic pitch” or the “avoid note.”  Two notes a half-step apart create a dissonant minor 9th interval, and since the fourth scale degree is a half step above the stable third degree, it is a point of instability in the major scale.  Chords in the subdominant family contain this fourth scale degree and include the IV and II minor chord.  In the table below, the fourth scale degree is italicized.

The chords in the subdominant family create a sense of motion.  Placing one after a tonic chord imparts a sense of departure.  The IV chord sounds a bit more stable than the II minor chord because of the former’s inclusion of the root (bolded in the table above).  Chords in the subdominant family can be substituted for one another.  It should be additionally noted that the VI minor chord can sometimes be used a subdominant chord when preceding the V chord.

Dominant Family

The seventh degree of the major scale is referred to as the “leading tone”.  Since the leading tone is a half-step (a dissonant minor 9th) below the root, it is the most unstable pitch in the major key.  Chords in the dominant family contain the leading tone and include the V chord and the VII diminished chord.  In the table below the leading tone is marked with an asterisk.

Chords in the dominant family create a sense of tension.  They are often used towards the end of a progression to return to a tonic chord.  The VII diminished chord is considerably more tense than the V chord, as it includes both the leading tone and the characteristic pitch (italicized in the table).  As such, it is not often utilized in its triadic form in pop music.  The V chord is frequently used to “cadence” to a tonic chord.

Using Chord Families to Create Chord Progressions

Chord progressions conventionally proceed from stability to motion to tension and finally back to stability.  The chord families above can be used to accomplish this task.  Let’s say we begin a progression with the I chord in C.  From here we typically have two options: remaining on a tonic chord or progressing to a subdominant chord.  Let’s say we choose to progress to the IV chord in the subdominant family.  Now our chord progression looks like this:

|C———|F———|

We now have the choice to remain on a subdominant family chord, regress to a tonic family chord, or progress to a dominant family chord.  Let’s say we choose to remain in the subdominant family and move to the II minor chord.  Now our progression looks like this:

|C———|F———|Dm———|

From here, it probably would be best to progress to a dominant chord as remaining in the subdominant family two long will ruin the sense of motion.  Let’s say we choose to progress to the V chord.  Now our progression looks like this:

|C———|F———|Dm———|G————|

Notice we have ended on a tense dominant chord.  This sets up to repeat the progression again by returning to the I chord.  The second time through, however, we might progress to the V chord in dominant family after the IV chord to set us up to return to I in the last measure and end with a sense of stability.

||C———|F———|Dm———|G————|

|C———|F———|G———|C————||

Please note how I have strived to emphasize the conventionality of this approach.  All ideas on writing music should be thought of as tools, not rules.  Composers and songwriters make all kinds of deviations from convention to best fit the aim of their song or composition.  In your favorite music, you will likely see many examples that contradict the ideas laid out here.  Still, I would advise all of my students to endeavor to master the conventional approach to music before experimenting with unconventional approaches.

In the following examples, identify the roman numeral function and family of each chord.  Each example begins on the I chord.

|| C———| Em ——— | Dm———| G———:||

|| G———| Am ——— | C———| D ———:||

|| F———| C———| Dm ———| Bb ———:||

|| D———| G—A—| Bm ———| G —A—:||

|| A—F#m—| D—E—| A —C#m—| Bm —E—:||

|| E— A—| B———| E— A—| B———:||

||Bb—F—| Dm—Gm—| Cm—F—| Bb———:||