The Structural Differences And Functional Similarities Between Primary And Secondary Chords In The Major Key

In today’s lesson we’re looking at the structural differences and functional similarities between primary and secondary chords in the major key.

We dedicated previous lessons to learn what primary and secondary chords are, and now it’s time to take you a step further by learning the structural and functional differences between them.

If you invest the next 15 minutes or so, you’ll be learning characteristic differences between major and minor chords in the major key.

A Review On Scale-degree Triads

There are eight degrees in every major key and triads can be formed on every degree of the scale. In the key of C major:

C is the first degree (aka – “the tonic”)

D is the second degree (aka – “the supertonic”)

E is the third degree (aka – “the mediant”)

F is the fourth degree (aka – “the sub-dominant”)

G is the fifth degree (aka – “the dominant”)

A is the sixth degree (aka – “the sub-mediant”)

B is the seventh degree (aka – “the sub-tonic”)

C is the eighth degree (aka – “the octave”)

“Check Out The Scale Degree Triads In The Key Of C Major…”

On the first tone (C):

…is the C major triad:

On the second tone (D):

…is the D minor triad:

On the third tone (E):

…is the E minor triad:

On the fourth tone (F):

…is the F major triad:

On the fifth tone (G):

…is the G major triad:

On the sixth tone (A):

…is the A minor triad:

On the seventh tone (B):

…is the B diminished triad:

Now that we’re done with scale degree triads in the key, let’s look at the primary and secondary triads.

A Quick Review On Primary Chords

Although there are so many ways to define a primary chord, let’s use the definition below:

Primary chords are chords that share the same quality with the key.

In the key of C major, all the triads that have the same quality with the key are primary triads. Due to the fact that the quality of the key is major, all major triads in the key can be considered as primary chords.

In the key of C major:

…major triads are triads of the first, fourth, and fifth degrees – which are the C major:

…F major:

…and G major triad:

These primary chords play the basic harmonic roles in the key especially the harmonization of the major scale and the accompaniment of melodies.

Suggested Reading: An Exposition On The Primary Chords In The Key.

A Short Note On Secondary Chords

Other scale degree triads that have a quality that differs from that of the key are known as secondary triads. There are three triad qualities among scale degree triads – the major triad, the minor triad and the diminished triad.

The diminished triad of the seventh degree is most times considered as an incomplete dominant seventh chord because of its instability. Notwithstanding that it’s a secondary chord, we’ll be focusing on secondary triads that have a minor quality.

In the key of C major:

…minor triads are formed on the second, third and sixth degrees.

“Check Them Out…”

The D minor:

…E minor:

…and A minor triad:

We’ll be talking about the harmonic roles of these secondary chords in the next segment.

Suggested Reading: An Exposition On The Primary Chords In The Key.

Primary Chords Vs Secondary Chords

From our review on primary and secondary chords, one can spot a quick difference in quality between both of them. Let’s go further by exploring the structural and functional differences between primary and secondary chords.

Structural Differences Between Primary And Secondary Chords

The structure of a chord is a product of the intervals that make it up (aka – “its intervallic constituents”.)

“Here’s The Structure Of Primary Chords”

Due to the fact that primary chords have the same quality with the key, all primary chords in the major key have a major quality. Hence, we’ll be using the C major triad as a reference to understand the structure of primary chords.

The C major triad:

…can be broken down into two third intervals…

C-E:

…a major third interval.

E-G:

…a minor third interval.

From our breakdown of the C major triad, we can see the structure of primary chords; a major third interval (C-E):

…before a minor third interval (E-G):

“Here’s The Structure Of Secondary Chords”

The quality of secondary chords differ from the quality of the key. In the major key, secondary triads are minor triads. The D minor triad:

…the chord of the second degree can be used to breakdown the structure of secondary chords.

The D minor triad:

…can be broken down into two third intervals…

D-F:

…a minor third interval.

F-A:

…a major third interval.

From our breakdown of the D minor triad, we can see the structure of secondary chords; a minor third interval (D-F):

…before a major third interval (F-A):

Now that we have an idea of the structure of primary and secondary triads, here’s the remarkable structural difference between primary and secondary triads:

In primary triads, a major third interval comes before a minor third interval, while in secondary triads, a minor third interval comes before a major third interval.

Irrespective of their structural differences, primary and secondary chords are functionally related. Let’s take a look at some of those similarities.

Functional Similarities Between Primary And Secondary Chords

In a previous post, we learned how secondary chords can function as subsidiary chords to primary chords.

A subsidiary chord is a chord that shares two or more notes in common with a given chord.

There are secondary chords that share two notes in common with primary chords in the major key and they play a subsidiary role to those primary chords. An example is chord six – the A minor triad:

…which has two notes in common with chord one – the C major triad:

So, chord one and chord six have two notes in common – C and E:

Beyond having two notes in common, can chord one and chord six be used in the same harmonic situation? The answer is Yes!

“Quickly! Let Me Show You The Subsidiary Chords Of Primary Chords…”

Primary chords in the key of C major are the C major triad:

…the F major triad:

…and the G major triad:

Each of these primary chords have their respective subsidiary triad whose root is a minor third below the given primary chord.

The root of the subsidiary triad of the F major triad:

…is a minor third below F:

…and that’s D:

Therefore, the D minor triad:

…is the subsidiary chord of the F major triad:

“Also…”

The root of the subsidiary triad of the G major triad:

…is a minor third below G:

…and that’s E:

Therefore, the E minor triad:

…is the subsidiary chord of the G major triad:

“In A Nutshell…”

Here’s the functional similarity between primary and secondary chords in the major key:

• Chord 6 is the subsidiary chord of Chord 1
• Chord 2 is the subsidiary chord of Chord 4
• Chord 3 is the subsidiary chord of Chord 5

…this means that a 1-4 chord progression, from the C major triad:

…to the F major triad:

…can be played as a 6-2 chord progression, using the A minor triad:

…and the D minor triad:

Final Words

I’m sure that you’ve seen the relationship between primary and secondary chords in another light, especially the difference in structure and similarity in function.

I’ll see you in the next lesson where we’ll explore other relationships that scale degree chords share – whether major or minor.

Thanks for your time.

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Chuku Onyemachi

Head of Education at HearandPlay Music Group

Onyemachi "Onye" Chuku is a Nigerian musicologist, pianist, and author. Inspired by his role model (Jermaine Griggs) who has become his mentor, what he started off as teaching musicians in his Aba-Nigeria neighborhood in April 2005 eventually morphed into an international career that has helped hundreds of thousands of musicians all around the world. Onye lives in Dubai and is currently the Head of Education at HearandPlay Music Group and the music consultant of the Gospel Music Training Center, all in California, USA.

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