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Contents:
• 7th Chords
• 7th Chord Notation
• Intersting fact about the full-diminished 7th chord

7th Chords

Now that we have a foundation for creating chords from the major scale, we can take it a step further and create 7th chords. The different types of 7th chords are Major 7th, Minor 7th, Dominant 7th, Diminished 7th, Half-Diminished 7th.

Using the C major scale again:
C D E F G A B C
1 2 3 4 5 6 7 8

If we take a C major triad (C E G) and add the 7th scale degree to the triad (which in this case is B), we will get "some kind of a 7th chord"... To figure out what kind of 7th chord, we need look at the distance from C to B, which is a Major 7th. Click here to review intervals. Adding a major 7th to a major triad (chord) will give a Major 7th Chord.

The next chord in the key of C major is the D minor chord. The 7th from D is a C (remember to use the notes from the C major scale), which is a minor 7th interval. Adding a minor 7th to a minor triad results in a Minor 7th Chord.

The next 7th chord will be built from the 5th scale degree, or the G note. The triad built on the G note is a G major triad, so let’s now look at the 7th, which is an F... This creates a rather odd chord, a major triad, but with a minor 7th. This is called a Dominant 7th chord, which gets its name because it is built off the 5th scale degree in the major scale (click here to refresh on the names of the scale degrees). The 5th scale degree is the only place that the dominant 7th chord will occur, and this is why it is given the name of dominant 7th.

The last type of 7th chord will be built off the 7th scale degree (B), which is the diminished triad (B diminished). There are actually two types of 7th chords that can be built off of a diminished triad. The first type is called a Half-Diminished 7th chord. Start with the diminished triad (Bdim) and add the 7th to this triad from the scale (which is an A note). This results in a diminished triad with a minor 7th, which is a half diminished 7th chord.

The second type of diminished 7th chord is called a Full-Diminished 7th chord or just Diminished 7th. In order to get a Full-Diminished chord the 7th has to be flatted again, (to Ab) this is called a bb7 interval (or “double flat”).

Therefore, the Half-Diminished can be created by stacking 3rds on the 7th scale degree of the major scale. In other words, using the C major scale, if you build a 7th chord on the 7th scale degree (B) you will get a B half-diminished 7th chord.

You may have noticed however that when we built the full-diminished chord, the “Ab” note was not in the C major scale. Therefore, the full-diminished chord cannot be built by stacking 3rds on the 7th scale degree of the major scale as we did before, because the bb7 is not in the scale. This chord can only be created by altering the 7th (flatting the 7th to make it a bb7).

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7th Chord Notation

Here is a list of common ways you will see the various 7th chords notated and abbreviated.

I'll use C chords to demonstrate.

Major 7th: Cmaj7, CM7
Minor 7th: Cmin7, Cm7
Dominant 7th: Cdom7, C7
Half-Diminished 7th: Cø7, Cm7b5
Full-Diminished 7th: Cdim7, Cº7, Co7

Note: The full-diminished will often have a degree symbol (º) and the half-dimished will often have a slash through the degree symbol.

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Intersting fact about the diminished 7th chord

There is something very unique and quite interesting that applies to the diminished 7 chord... Because each interval is the same distance apart, you can actually treat any note as the root note and thus change the name of the chord without changing any of the notes in the chord. The following will help illustrate this point:

First off, since there are only a total of 12 notes that you can play, you'd likely agree that there has to be 12 full diminished 7 chords.... (just like there are only 12 major chords, 12 minor chords, etc.)

Now we'll start on A and create a diminished 7 chord:
A C Eb Gb

Now since the intervals are spaced out evenly, you can rearrange the chord by choosing a different note to be the root note like this:
C Eb Gb A

Now instead of being an A diminished 7 chord, this chord is a C diminished 7 chord. You can also change to be either an Eb diminished 7, and a Gb diminished 7.

Therefore, one diminished 7 chord is actually four different diminished 7 chords rolled into one. So since there are a total of 12 full diminish chords and each individual chord is four chords in one, there are only a total of three dimished 7 chords before you start repeating (12 / 4 = 3).

Here is a complete chart, so you can see that all 12 diminished 7 chords can be represented by these three chords. Don't just take my word for it, make sure that you try to find all twelve chords (from A to G#) in this list.

A C Eb Gb
- A diminished 7
- C diminished 7
- Eb diminished 7
- Gb diminished 7

A# C# E G
- A# diminished 7
- C# diminished 7
- E diminished 7
- G diminished 7

B D F Ab
- B diminished 7
- D diminished 7
- F diminished 7
- Ab diminished 7

As you can see, the diminished 7 chord is a never-ending cycle of minor 3rds. It is because of this that you can pick any note in the chord to be the “root note” and the notes in the chord won’t change, thus the chord’s sound stays the same even though it has a different root note. You can’t do this with any other chord chord. For example spelling out a C major chord and picking one of the notes in that chord to make another major chord would result in different chords.

C major = C E G
E major = E G B
G major = G B D

While these chords may have some similar notes, they are not “identical” and that is why this method only works with the full-diminished chord.



* Next Lesson: Chord Substitution