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Chords of Major Keys: Major, Minor & Diminished Triads

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Every major key has a set of 'native' chords that can be formed by combining notes of the major scale of that key. Before we look at how the chords are formed in more detail, though, first, let's look at what a major key means.

When we talk about a song being in a major key such as C major, for example, it means two things:

  1. Most, if not all, of the notes (melody, bass and chord tones, etc.) in the music will also be found in the C major scale. A simple song might not use all the notes of the scale, whereas a more complex song or composition might use all of them plus a few foreign notes borrowed from other sources. It may even change key more than once and the notes would then agree with different major (or minor) scales.
  2. It also means that the music has been composed in such a way that the note C and the chord C major will be heard as the most important note and chord of the music. They're called the key note and chord or tonic note and chord. Both the tonic note and chord will have a feeling of stability about them, and when placed at the end of the music, or section, verse or chorus, etc., a strong feeling of finality. They're sometimes also called the home note or chord because of the feeling of coming home that we experience when we hear them.

Building Chords From Scale Notes

Chords belonging to any key can be produced by combining at least three alternate notes of that key's scale. Alternate in this context means we take each note of the scale, in turn, miss the next one, take the next, miss the one after that, and so on. We can keep doing that until we run out of scale notes, but for the purposes of this article, we'll limit ourselves to just three notes. This will give us a set of seven chords, which are called 'triads'—one built on every note of the scale.

We'll use the key of C major as our example, but the principle applies equally to all major keys. It also applies to all minor keys, but those will be dealt with in their own article.

The C major scale

The C major scale

Building the First Chord

As mentioned, triads are built by combining scale notes spaced three letters apart—or every alternate scale note. The first triad that we can make is formed by starting on the first scale note C, skipping D, which brings us to E, the 3rd scale note, skipping F, which brings us to G, the 5th scale note. That gives us the notes C, E & G, the notes of our first chord.

Highlighted notes, C E & G of the first scale chord

Highlighted notes, C E & G of the first scale chord

Now we have to name that chord.

As it's based on the note, C, this is some kind of C chord. To know what type of C chord it is, we have to look at the spaces (or intervals) between the notes C, (called the root of the chord) E (called the 3rd of the chord) & G (called the 5th of the chord).

The interval between C & E is called a 3rd because it spans 3 letters (C, D & E).

The interval between E & G is also called a 3rd because it too spans 3 letters (D, E & F).

However, these two 3rds are not equal in size. If you know about semitones (or half steps), you can see that C to E is an interval of 4 semitones or half steps, while E to G is only 3.

C (C#) (D) (D#) E (F) (F#) G

You can see how C to E is wider than E to G.

As one is larger than the other, we differentiate them by calling the larger one a major 3rd, and the smaller one a minor 3rd.

So our first chord is composed of a major 3rd (C to E) plus a minor 3rd (E to G).

Chords with that structure are called major triads. So the first chord is named C major.

Although the chord contains 3 different notes, in practice any of those notes can be doubled at any octave without changing the chord's name. However, if any other note is added apart from C, E or G, the chord will no longer be C major but something else. The same principle applies to all the chords listed here.

In other words, if you play these notes on a piano, you have the triad C major.

  • C E G = C major - it contains all three essential notes of the chord.
  • C G E G E G C E = C major because it contains nothing but C, E and G notes. The order of notes and the number of notes doesn't change anything. It's still the triad C major. We don't even have to start with C as our lowest note. We could start with E or G; it's still C major, but we say it's 'inverted' in that case rather than in 'root position' when C is the lowest note.
  • C E G C G B E C E is not C major because it contains the note B, which doesn't belong to C major.

Building the Second Chord

If we go through exactly the same process but starting on D, we get the notes, D, F & A as follows:

Highlighted notes, D, F & A of the second scale chord, D minor

Highlighted notes, D, F & A of the second scale chord, D minor

Again we have two intervals of a 3rd (D to F and F to A). This time, however, it's a minor 3rd followed by a major 3rd, the opposite of our first chord. You can see below how D to F is smaller than F to A.

  • D (D#) (E) F (F#) (G) (G#) A

Chords with this structure are called minor triads, and the name of this chord is D minor.

The Full Major Scale Triad List

If we repeat the procedure for every note of the scale, we have a table of chords containing all the triads that belong to the key: Remember that C major is just our chosen example. The order of chord types is exactly the same for every major key.

Note that building chords on G, A or B, it takes us beyond our one-octave scale. It's not a problem; we just continue the scale beyond the octave as required: CDEFGABCDEF etc.

Scale Degree Chord Table


The Chord Table (Explanation)

  • Column 1 is the scale degree and chord number. By convention, in music analysis, we use uppercase Roman numerals to specify major and augmented chords, and lowercase Roman numerals for minor and diminished chords.
  • Column 2 contains the notes (or chord tones) that combine to produce the chord.
  • Column 3 is the chord name consisting of the root note plus chord type. The order of chord types should be memorised (maj, min, min, maj, maj, min, dim) so that you can apply them to any major scale to quickly find all the chords of that key.
  • Column 4 is the interval structure; M3 = major 3rd and m3 = minor 3rd.
  • Column 5 is the technical name of each scale degree, which describes the function of the chord.

Notice the last chord is different. Both intervals are minor 3rds. Triads with this structure are called diminished. One more type of triad exists but isn't included here as it doesn't occur naturally in major keys. That's the augmented triad, which is composed of two major 3rds.

Chord Functions and Progressions

Here is a brief explanation of the function that chords usually have in music in major keys.

Chord I > Tonic (Major)

This chord, being based on the tonic note mentioned in the opening paragraphs, has the same feeling of stability and finality. Most songs will end on this chord. This chord is considered to be the tonal centre of the music. Composers and songwriters create musical and emotional variety by moving to and from this chord.

Chord II > Supertonic (Minor)

This is named from its position above the tonic. Its most common function is to lead to chord V, the dominant chord, in which case its function is said to be predominant.

Chord III > Mediant (Minor)

This scale degree is named from its position halfway between the tonic and dominant. The mediant chord is considered to be quite variable in function.

Chord IV > Subdominant (Major)

This is a very important scale degree and chord. It generally leads away from the tonic chord. Many song choruses start with this chord. This chord, like chord II, also can have a predominant function.

Chord V > Dominant (Major)

This is the most dynamically important chord of the key. It creates an expectation in the listener to return home to the tonic. It's often modified and made even more dynamic by adding another note that makes the chord no longer a triad, but a so called dominant 7th chord, labeled, V7. In our example key of C major, that chord would be called, simply, G seventh (G7) with notes G, B, D & F.

Chord VI > Submediant (Minor)

This is so named because it lies as far below the upper tonic as the mediant lies above the lower tonic. The submediant chord is closely related to the tonic.

Chord VII > Leading Note

This, like the dominant chord, has a strong tendency to lead back to the tonic. It's relatively rare though as the dominant 7th chord does the same job more convincingly. It's quite rare in pop and rock music but finds uses in classical music. In other types of music it's usually extended with other notes similar to how the dominant chord is extended by another 3rd to make it a dominant 7th chord, as mentioned above.

Primary Triads

Chords I, IV & V are the most important chords in any key and are known as the primary triads. A lot of music is written using these chords alone. The whole major scale of the key is contained within these chords. The other triads are called 'secondary triads' - important in their own way but not as important as the primary triads.

Questions & Answers

Question: In terms of notes, which chord is the second most important chord in a key?

Answer: After the tonic or 'home' chord, the dominant chord is the next most important. It's a bit like chess. The king is the most important, but it doesn't do much - moving just one space at a time. The queen is second most important, but it has great power and can move all over the board. That's why I say the dominant (especially the dominant 7th) is the most 'dynamically' important. It can force strong movement to the tonic chord to establish and strengthen the tonic chord's function as the tonal center.

© 2011 Chas Mac