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Chord Construction : 2) Seventh Chords
Bernard McDonagh

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Let's recap the formula for the major scale:

Tone – Tone – S/tone – Tone –Tone – Tone –S/tone

Ex 1: C – D – E – F – G – A – B – C

Ex 2: Ab – Bb – C – Db – Eb – F – G – Ab

We know that we can “harmonize” the major scale by stacking “thirds” on each degree, thus building the seven diatonic (naturally occurring) triads from the scale. We used the example of C Major but we know the principles apply to every major scale, regardless of how many sharps or flats it may have.

In C Major the II (two) chord is D Minor; In Ab the II chord is also minor – Bb Minor. Chord IV (four) in C Major is an F chord (major); Similarly, Chord IV in Ab Major is also major – but of course this time it is Db Major, etc.

Both of the examples above are major scales. Therefore when they are harmonized, even though the chords themselves will be different, they will have the same TYPE of chords on each degree.

CHORD TYPE

SCALE DEGREE

MAJOR

I — IV — V

MINOR

II — III — VI

DIMINISHED

VII

Though this is true and entirely consistent for every key, it would be clear to most of us that there are many more chords to be found than these basic three note triads. This leads us to the next step in chord construction: ‘seventh' chords .

Let's first check our foundations. It's important to go through this again, so that it will be clear. All ‘harmonization' happens the same way, whether we are forming diatonic triads or seventh chords, and as we shall see some time later, all the other kinds of chords as well.

Degree: I – II – III – IV – V – VI – VII – VIII

Note : C – D – E – F – G – A – B – C

Now that we have our scale we can “stack” our thirds and find our diatonic triads; staying for now with C Major:

Scale Degrees

Notes

Resulting Triad

Written as

 

 

 

 

1 - 3 - 5

C - E - G

C major

C

2 - 4 - 6

D - F - A

D minor

DMI

3 - 5 - 7

E - G - B

E minor

EMI

4 - 6 - 8

F - A - C

F major

F

5 - 7 - 2

G - B - D

G major

G

6 - 8 - 3

A - C - E

A minor

AMI

7 - 2 - 4

B - D - F

B diminished

 

 

 

 

When we now add a fourth note (which is also a “third” above the last note of the triad) on top of the basic triads some wonderful things begin to happen! Check it out!

Scale Degrees

Notes

Resulting Chord

Written as

 

 

 

 

1 - 3 - 5 - 7

C - E - G - B

C major 7th

CMA7

2 - 4 - 6 - 8

D - F - A - C

D minor 7th

DMI7

3 - 5 - 7 - 2

E - G - B - D

E minor 7th

EMI7

4 - 6 - 8 - 3

F - A - C - E

F major7th

FMA7

5 - 7 - 2 - 4

G - B - D - F

G dominant 7

G7

6 - 8 - 3 - 5

A - C - E - G

A minor 7th

AMI7

7 - 2 - 4 - 6

B - D - F - A

B min 7 flat 5

BMI7b5

 

 

 

 

Some very interesting things that have happened! Probably the most significant thing has occurred on degree V. The ‘Dominant' 7th chord, and in fact the whole Dominant chord family, has come into existence here on the 5th degree of the major scale! The dominant chords are extremely significant and important chords.

The principles involved in the construction and naming of 7th chords apply to every major scale just as they do for the triads. Each major key will have the same diatonic harmony when it comes to 7th chords also. i.e. Scale degree II in any major key will always produce a “Minor 7th ” chord. Degree VII will always produce a “Minor Seven Flat 5” chord, etc. For example, if we harmonized the Ab Major scale we wrote out earlier, we can be sure that the diatonic seventh chords will be:

AbMA7 - BbMI7 - CMI7 - DbMA7 - Eb7 - FMI7 - GMI7b5

 

Click here for our course on harmony

© 2004 Bernard McDonagh
Email : author@gsus.biz
http://www.gsus.biz


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