Exposed: The Eight Components In A Key Every Musician Should Know

There are eight components in a key – whether major or minor.

It’s ABSOLUTELY impossible for a key to remain a key if any of these components are missing and this is because each component has its unique function and role in a key.

It’s sad to know that only a handful of music scholars and aware of these components. I really count myself fortunate to know these components and that’s why I’m excited to share them with you.

If you give me your undivided attention for the next 16 minutes or so, you’ll not only discover these eight components, you’ll learn a lot about them.

A Short Note On The Concept Of Key

There are twelve musical notes:

The establishment of one of these notes as a principal tone, with other tones having their unique relationship with it produces a key.

The establishment of a key requires eight notes. For example, the establishment of the note C:

…as a key requires eight notes.

C:

…and these notes:

…altogether, establish the key of C major:

…while C:

…and these notes:

…altogether, establish the key of C minor:

“In A Nutshell…”

The establishment of a note as a key, creates what music scholars call tonality, which can either be major or minor. This explains why there’s a major and a minor key.

The First Four Components Of A Key – Explored

Let’s explore these four components:

Tonic

Dominant

Mediant

Supertonic

The Tonic

The first and most important note in a key is the tonic. In the key below:

…the first note is Bb:

…which by virtue of its position as the first note in the key, is the most important note – the tonic.

The tonic is the key center and literally the center of attraction in every key – whether major or minor. Every other note gravitates towards it.

The letter name of any given key is derived from its tonic. The tonic in the key below:

…is E:

…consequently, it’s the key of E.

You can spot the tonic in any given key because of its conspicuous position as the first note in a key. So, always keep an eye on the first degree in the key because it’s the center of attraction.

The Dominant

The dominant is the fifth degree in a key and the next component of a key in terms of importance. The dominant in the key of C major:

…is G:

…which is the fifth tone of the C natural major scale.

The dominant is an important tone for a variety of reasons and here are two of them:

There are three stable tones in a key – the first, third and fifth tones of the scale – and the dominant (the fifth tone) happens to be one of them.

The chord of the fifth degree (aka – “the dominant chord“) has the strongest affinity for the first degree (aka – “the tonic chord“). Consequently, the dominant chord is used to establish or contradict a key and is usually used in the change of key (aka – “modulation”).

In a nutshell, the importance of the dominant CANNOT be over-emphasized. Believe it or not, no key is complete without the dominant because the establishment of a key depends on it.

The Mediant

The term mediant literally means ‘come between’ or ‘be in the middle of’ and is associated with the third component in the key and this is because it lies between the tonic and the dominant.

In the key of C major:

…the tonic (first tone) and dominant (fifth tone) are C and G:

The third tone (which is E):

…that is in the middle of C and G:

…is the mediant.

The mediant is also a very important key component and this is because together with the tonic and dominant, it produces the tonic triad – which is a collection of stable tones in the key.

In the key of C major:

…the mediant (which is E):

…together with the tonic (which is C):

…and the dominant (which is G):

…produces the C major triad:

…the tonic triad in the key of C major.

The Supertonic

The prefix super literally means ‘to place or be placed above or over.’ When applied to the term tonic, we’ll have the term supertonic – which means a note that is placed above the tonic.

In the key of C major:

…D:

…is the supertonic and this is because it is the component of the key that is placed above the tonic (which is C):

The supertonic can easily be identified in any key by virtue of its position as the second degree in the key, placed above the tonic. In the key of B major:

…the supertonic is C#:

…and this is because it is the second degree, placed above B (the tonic):

“Take Note…”

The chord of the supertonic is known as the pre-dominant chord, and this is because it is usually played before the dominant chord in chord progressions.

The Last Four Components Of A Key – Explored

The Octave

The octave is the eighth component in a key. The prefix oct connotes eight and can be seen in other words like octagon (a shape of eight sides), octopus, and so on.

The octave is exactly eight tones from the tonic and is a duplicate of the tonic. In the key of C major:

…the octave (which is C):

…is a duplicate of the tonic (which is also C):

It’s easy to determine the octave because it has the same letter name with the tonic.

The Subdominant

We came across the term dominant in the previous segment which lies a fifth above the tonic. The subdominant is the component of a key that is a fifth below the tonic.

A fifth below the tonic (in the key of C major):

…is F:

…which is the fourth tone of the scale.

“Take A Closer Look At This…”

Here’s the tonic:

…a fifth above it:

…is the dominant, and a fifth below it:

…is the subdominant.

The term subdominant can be broken down into sub which means below and dominant which means fifth. Therefore, the term subdominant literally means “a fifth below.”

The Submediant

The term mediant is not new – we came across it earlier in this lesson. The submediant is the key component that is between the tonic and the subdominant.

In the key of C major:

…the tonic and subdominant are C:

…and F:

…respectively, and between them is the submediant (A):

…which is the sixth tone of the C natural major scale:

The Subtonic

The term subtonic is self-explanatory – sub means below while tonic is the technical name of the first degree of the scale. The subtonic is the seventh degree in the key and is a step below the tonic.

In the key of C major:

…where C is the tonic:

…and octave:

…the key component directly below the tonic:

…is the subtonic.

Final Words

Having learned the eight components of a key, it is expected that you apply the terms learned in real life. Using the key of C major:

…as an example, you can use the term mediant to refer to E:

…instead of making reference to it as the third tone (which is still absolutely correct).

Thank you for your time and I’ll see you in another lesson!

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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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