Guide to Chord Formation : 7th Chords

Guide to Chord Formation by Howard Wright (Howard@jmdl.com)
Chapter 4 : 7^th Chords

4.0 : 7th Chords

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4.1 : Minor 7ths

For minor chords there is one common type of 7^th - the minor 7^th. As you might expect, you start with the minor triad, then add the minor 7^th.

So, as an example lets take D minor 7^th (Dm7).

The spelling is: 1^st, minor 3^rd, 5^th, minor 7^th.
Using the table of intervals above, we count up from D to get the other notes.

To get the min 3^rd, count up 3 semitones - F
To get the 5^th count up 7 semitones - A
To get the min 7^th count up 10 semitones - C

So Dm7 is made up of the notes: D F A C

If you use the open D string for the D note, you could use these two shapes:

  EADGBE     EADGBE
  xx0211     xx0565

   Dm7        Dm7

Min/maj 7^th chords

There is another chord called the min/maj7^th. This is a bit of a weird fish, but you might come across it once in a while. It's made up by taking the minor triad and adding the major 7^th to it.

So Dm/maj7^th would be: D F A C^#

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4.2 : Major 7^ths and flat 7^ths (dominant 7^ths)

With major triads you can build two types of 7^th chord. If you add the major 7^th of the scale, you get the major 7^th chord. If you add the flat 7^th to the major triad you get the so-called dominant 7^th chord.

When guitarists talk about '7^th chords' as in 12-bar blues etc, then they mean chords with the flat 7^th.

Major 7^th chords are written as Cmaj7, Dmaj7 etc., but the flat 7 or 'blues' 7^th is written simply as C7, D7 etc.

So for a major 7^th chord the spelling is:

1^st major 3^rd 5^th major 7^th

If we start with F as our root and count up, we get this:
Go up 4 semitones from F for major 3^rd: A
Go up 7 semitones from F for 5^th: C
Go up 11 semitones from F for maj 7^th: E

So the notes of the chord Fmaj7 are: F A C E

To build an F7 chord, the only difference is that we add a flat 7 instead of a maj7. So we add an E^b instead of E, so the notes of a F7 chord are: F A C E_b

As with simple triads, you can double up on some of the notes to make a chord. With 7^th chords you could double up on the root, 3^rd, 7^th or 5^th.

Take a standard 7^th chord, E7:

    EADGBE
    020100

The notes are: E B D G^# B E, so the root and 5^th have both been doubled.

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Guide to Chord Formation by Howard Wright
Reformatted and noded (with permission) by Space Butler
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