Guitar Music Theory 102

Guitar Music Theory 102 is a continuation of Guitar Music Theory 101 and should be used in conjunction with Ear Training 101 etc.

Lesson 11

Constructing 7th Chords

In Guitar Music Theory 101 you learned how to construct triads from a major scale.

Once you know how to construct triads from a major scale, constructing seventh chords is super easy.

As you know triads are constructed by intervals of a third.

The C major scale is C D E F G A B

The C major triad is spelled C E G.

The D minor triad is spelled D F A.

To construct a seventh chord you simply take a triad and add an interval of a third on top of the triad.

So, the C major triad spelled C E G becomes a C seventh chord spelled C E G B.

The D minor triad spelled D F A becomes a minor seventh chord spelled D F A C and so on.

Two Types of Seventh Chords

There are two types of seventh chord and these two types of seventh chords seem to confuse a lot of people.

The two types of seventh chords are the dominant seventh chord and the major seventh chord.

When you went up by the interval of a third to construct a triad some distances from the root note to the third were either a minor third or a major third.

The minor third resulted in a minor triad and the major third resulted in a major triad.

You can see the C major triad has a major third interval from the root note C to the third of E. The major third interval is a distance of 4 frets. Hence the notes C E G spells a C major triad.

For the D minor triad the distance from the root note of D to the third of F is a minor third or a distance of 3 frets. This is why the D minor triad is a minor triad and not a major triad.

So it is with seventh chords.

There are a few different ways to think about this but let’s extent the C triad to include the 7th.

C triad = C E G

C Major 7th Chord = C E G B (Cmaj7)

The major in C Major 7th Chord relates to the 7th of the chord. The B note is one semitone away from the root note of C so it is a major 7th interval from C.

D triad = D F A

D minor 7th chord = D F A C (Dm7)

The interval from D to C is a minor 7th. The minor 7th is also known as a flat 7th or b7th.

The chord name shows that it’s a type of minor chord with a flat 7. If the minor chord has a major seventh it would be notated as Dm(maj)7. This type of chord is found in the melodic and harmonic minor scales which will be discussed later.

If we continue this sequence we get the following chords (from the C maj7 chord);

• Cmaj7 (CEGB)
• Dm7 (DFAC)
• Em7 (EGBD)
• Fmaj7 (FACE)
• G7 (GBDF)
• Am7 (ACEG)
• Bdim7 (BDFA)

There are a few things to note.

• There are 2 major 7th chords. The first chord and the 4th chord which are the C and F chords.
• There are 3 minor 7th chords. The Dm7, Em7 and Am7.
• There is one dominant 7th chord which is the fifth chord the G7.
• The Bdim7 can also be described as a B half diminished chord. In a full diminished chord the 7th note is actually a bb7 so in the case of the Bdim7 the 7th note of A would actually be Ab.

The G7 chord has a very strong pull towards the C chord. In other words the Five chord (V in roman numerals) has a very strong pull to the One chord (I in roman numerals) that is way you see loads of songs moving from G7 to C especially at the end of sections such as verses and choruses etc.