Dahnielson

Chords

A chord, as you already may know, is made up of an interval of tones played simultaneously. The most basic chord formation is a triad using an interval of thirds, consisting of the root, 3rd and 5th:

The chord above is a C major (or just C for short) since the root give name to the chord. And it’s a major chord since it contain a major 3rd.

While a minor 3rd makes the above to a C minor chord (or Cm for short).

Each note has a function within the chord, the note the chord is built on is called the root of the chord, the second note a third above it is called the third of the chord, and the third note a third above the second note is called the fifth of the chord. This is true of all triads, regardless of key, inversion, or quality.

This means that you for example can play the C major chord in any way of the below:

It’s still the same chord, only inversed to the first, second and third degree.

Interval

When talking about 3rd’s, 5th’s, and so on in chords we’re talking about intervals. What kind of interval it is depend on whether the semitone interval appear diatonic in a minor or major key.

To illustrate the logic behind it let’s play the intervals in two different keys, using the scale tonic as root. First play the 3rd, and then the 5th in C major:

Now do the same in A minor:

First we will note that the above intervals are all diatonic, meaning they only use notes belonging to the scale of the key we played in. Now count the number of semitones. You’ll find that 3rd’s are always four semitones in major keys, that’s why it’s called a major third, while being three semitones in minor keys, hence the term minor third. The same pattern are true for 5th’s and any other interval.

To diminish an interval means to alter it by lowering the pitch a semitone. For example, a diminished major fifth will yield the same interval as a minor fifth in practice. But it’s still a major that has just been diminished.

Quality

Jazz rarely use triads, with the exception of occasional minor chords. Because they usually does not sound “thick” enough lacking interesting harmonies. So for example a 7th is added to the C chord, making it a Cmaj7:

There are basically four chord qualities used in jazz we need to know about for now, they are: major 7, dominant 7, minor 7 and half diminished. Here illustrated by being applied to a C chord:

They are simple to figure out for any key by keeping the following in mind:

• All Major 7 chords has major 3rd and major 7th.
• All Dominant 7 chords has major 3rd and minor 7th.
• All Minor 7 chords has minor 3rd and minor 7th.
• All Half Diminished chord has minor 3rd, diminished 5th and minor 7th.

And just for the record, there’s also two less common qualities, minor major 7 and diminished 7, occasionally used when playing in minor keys:

• All Minor Major 7 chords has minor 3rd and major 7th.
• All Diminished 7 chords has minor 3rd, diminished 5th and diminished minor 7th.

Extended Chords

We’ve already seen the common practice in jazz of adding a 7th. But there’s nothing to stop us from extending chords upwards by adding interval of thirds:

The example above show how we can extend major, minor and dominant chords with 9th, 11th and 13th’s (technically speaking a 7th isn’t an extended chord.) Of course there is endless possibilities to also diminish and otherwise alter the chord extensions. But it’s not the place to dwell deeper into here. Just note that dominant chords have greater scope for extensions and alterations than major and minor chords, because the latter resulting dissonance is often undesired.

Diatonic Chords

Major Harmony

Now we try to play a scale of chords by only using notes we find in a specific key. Let’s start simple and do it in C major:

The correct term to describe what we just did is that we played chords functioning diatonically within a key. And we can simply call the scale above diatonic chords of C major.

And here are diatonic four-note chords in rest of the major keys:

As you may already have noticed, all chords follow a distinct pattern no matter what the key is. That’s right, the progression of chord qualities is the same! With this fact in mind it’s possible to memorize common chord progressions as numerals and play them in any major key. So instead of writing a chord progression as Dm-G7-Cmaj7, we can memorize it as II-V-I.

Minor Harmony

Now the question begs, can we create a scale of chords diatonically within a minor key? Well, minor harmony is slightly more complex since we have both harmonic and melodic minors. But it’s good to keep in mind that the alterations to the 6th and 7th degrees of the natural minor scale were made for melodic reasons, not harmonic.

In practice this means we need a combination of chords based on harmonic minor harmony with some borrowed chords from Dorian or Aeolian modes to construct a scale. Here in A minor:

Even if minor harmony are more complex than major harmony it also allow for a great deal of variety with the alternative 6th and 7th degree chords. And here are four-note chords in rest of the minor keys:

As previously stated, minor harmony can be a little bit difficult. So let’s just stick to major keys for now.