Chord Notation - Basics

Chord Notation - The Basics

Triads

Chord notation, as it appears in Western music,  is based on scales.


The main musical scale of Western music is the major scale, shown above for the key of C. Using each note in the scale as a starting point, we can construct a triad (three note chord) by combining it with the note two steps above it, and the note two further steps above:


Why two steps? Because these combinations are pleasing to the ear. Triads I, IV and V have a sound that it often described as 'happy'. Triads ii, iii and vi have a 'sad' sound. Triad vii has a tense, unresolved sound.

What triads I, IV and V have in common is that they share the same interval structure between notes. Between the bottom and middle notes is an interval of a major third, or 4 semitones. Between the middle and top notes is an interval of a minor third, or three semitones. We call these major chords.

Triads ii, iii and vi, on the other hand, have an interval of a minor third between the bottom and middle notes, and major third between the middle and top notes. These are minor chords.

Triad vii, the one with the unresolved sound, has a minor third between both bottom and middle, and middle and top. This is a diminished chord.

These chords are named by their bottom (root) notes, so:

• I = C major
• ii = D minor
• iii = E minor
• IV = F major
• V = G major
• vi = A minor
• vii = B diminished

In practice, musicians usually refer to major chords just by the root, so they will say "G" rather than "G major".

What about a triad that has a major third between bottom and middle, and middle and top? Here is such a chord:


We call this an augmented chord - note that it includes a note that does not appear in our scale.

Augmented chords have a 'floating' quality and, like diminished chords, sound as though they want to resolve to something else (a major or minor chord).

So we now have the basis of the four types of triads that typically appear in Western music - major, minor, diminished and augmented.

Inversions

Because the same notes are repeated in different octaves, it is possible to have the same three notes in different ways:

The above shows a C chord (that's C major) in three different positions - the same three notes are used (C, E and G), but in different octaves. These arrangements are called inversions. Notice that in the inversions, the intervals between notes have changed, and we now have intervals other than major or minor thirds.

Seventh Chords

Using the triads as a starting point, we can construct other chords involving more than three notes.

Our basic C chord consists of the first, third and fifth notes of our C scale. We can add the seventh note of our scale to form a seventh chord:


If instead we started at the G in our scale, treating it as the first note of the scale and combined it with the third, fifth and seventh, we get this seventh chord:

The sounds of these two chords are noticeably different - the difference lies in the interval between fifth and seventh. In our first seventh chord, built on the C root, the fifth and seventh are a major third apart, but in the second seventh chord, built on G, the fifth and seventh are a minor third apart.

We call the first chord a major seventh chord, in this case, C major 7 (usually written on music as Cmaj7 or C∆7).

 The second is still a major chord (because the basic triad of root-third-fifth is major chord), but in this case we call it a dominant seventh chord. Why 'dominant'? Because the fifth note of a scale is called the dominant. Often when referring to dominant seventh chords, the word 'dominant' is omitted. So in the case of our second chord above, we would call it G7 (and write it that way as well).

So from a major triad, we get two types of seventh chord, the major seventh and dominant seventh.

Going back to our scale again, our minor chords were build from D, E and A. Constructing seventh chords from the triads with those roots, we find that they all have an interval of a minor third between the fifth and seventh:

So these are minor seventh chords, D minor 7,  E minor and A minor 7, and would be written as Dm7, Em7 and Am7.

Going back to scales for a moment, Western music also has a minor scale, shown here for the key of A minor.

Here we see two versions of the scale for A minor. The first version shows the notes of the scale as per the key signature. In the second version, the seventh note of the scale has been raised a semitone. Raising the seventh like this has been seen in Western music since the time of Bach - it changes the final step from seventh to root from a tone to a semitone, so that resolution from seventh to the root sounds more finished; the chord built on the fifth note of the scale becomes a major chord rather than a minor one, and moving from a major chord on the fifth to the minor chord on the root again has a more finished sound.

The seventh chord built on the root of this scale has a major third between the fifth and seventh:

We call this a minor major seventh chord. (We would write Am maj7 or Am∆7.)

Finally, we will look at the diminished seventh chord:

This chord is based entirely on intervals of a minor third. For this example,  the chord would be called C diminished 7 and written Cdim7 or Co7.

The interesting thing about diminished seventh chords is that different diminished seventh chords are inversions on one another. For example, Ddim7, Fdim7, A♭dim7 and Bdim7 are all the same chord!

There is also a chord often referred to as a half-diminished seventh:

This is also based on the diminished triad, but the seventh is a major third above the fifth rather than a minor. Another, perhaps better, description for this chord is a minor seventh with a flattened fifth. The example above might be called a "C half-diminished 7", or a "C minor 7 flat 5". In written form, the most common notations are Cø7 or Cmin7♭5.