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