the Diminished Seventh Chord (o7)

Some Review

Recall from lesson on creating a context that we've defined a chord as being 3 or more distinct notes, usually played at the same time. (C and D are considered distinct, but C# and Db are not, nor are octaves of the same note).

Recall that chords come in two basic parts, a letter name (C, C#, etc.) also known as a root note (tonic, 1), and a descriptive part that abbreviates the name of the chord (is a short-hand for all the intervals of each distinct note from the root note).

Recall that an interval is the distance between two notes, and that we are using numbers (with accidentals) to describe these intervals.(ex. 5 = perfect fifth, etc.) For more info on intervals see July19's lesson. to convert letters to numbers and numbers to letters, see the link below (bottom of page) on transposition.

Recall, we've previously defined the following chords:
major = 1,3,5
minor (m)= 1,b3,5
diminished (o)= 1,b3,b5
power chord (5) = 1,5,8(1)
dominant seventh chord = 1,3,5,b7
minor seventh chord = 1,b3,5,b7
major seventh chord = 1,3,5,7
half-diminished seventh chord = 1,b3,b5,b7

Now we shall define the diminished seventh chord as:
o7 = 1,b3,b5,bb7
Sometimes we write diminished seventh chords as o7, or dim7 . (Ex. Cdim7, Co7 etc.)

Sometimes the Diminished seventh chord is refered to as a fully-diminished seventh chord, in order to make sure that there is no confusion between the diminished seventh chord, the half-diminished seventh chord, and the diminished chord (diminihsed triad).

Further many jazz players assume certain extensions on certain chords when abbreviated in jazz/pop notation.

for example, jazz players would read :
C- as Cm7
Cmaj as Cmaj7
and Co as Co7

In a classical theory textbook, they would clearly define o as being the diminished triad, and o7 as being the diminished seventh chord.

Since there exists confusion amoungst players out there, I suggest using the terms diminished triad, half-diminished seventh chord, and fully-diminshed seventh chord when speaking with other musicians to minimize any confusion.

Here are some open o7 chords to get you started:
Bbo7=012020,Do7=XX0101,F#o7=201X1X .

Since the o7 is symmetrical
Bbo7 = Dbo7 = Eo7 = Go7
Ao7 = Co7 = Ebo7 = F#o7
Abo7 = Bo7 = Do7 = Fo7

We should note from our definition (o7=1,b3,b5,bb7) that a diminished seventh chord contains a diminished chord (diminished=1,b3,b5) within it. We can think of a diminished seventh chord as a diminished chord with an added diminished seventh note.

If we don't know how to play a o7 chord, we could substitute a diminished chord with the same root note in its place. We will no longer have the full flavor of the o7 chord, but the substitution should work.

We also note that a chord synonym for for io7 is biiio7. In the key of C:
Bo7 = B,D,F,Ab = 1,b3,b5,bb7
Do7 = D,F,Ab,B = 1,b3,b5,bb7

So you could use as a substitute for a o7 chord, a diminished seventh chord a minor third higher than the m7b5 chord. (you could substitute Do7 for Bo7)

So you could use as a substitute for a o7 chord, a o7 chord a minor third higher than the o7 chord, or a diminished fifth higher, or a major sixth higher {more on this below}. (you could substitute Co7 for Ebo7 or Gbo7 or Ao7)

* The diminished seventh chord is symmetrical, so it inverts upon itself.

Recalling how the chromatic scale maps out on a fretboard in standard tuning ( see July19's lesson). We can map out the o7 chord on the fretboard (shown here in F).

|-1-|---|---|b3-|---|---|b5-|---|---|bb7|---|---|--1|
|---|---|bb7|---|---|-1-|---|---|b3-|---|---|b5-|---|
|b3-|---|---|b5-|---|---|bb7|---|---|-1-|---|---|b3-|
|---|---|-1-|---|---|b3-|---|---|b5-|---|---|bb7|---|
|---|b5-|---|---|bb7|---|---|-1-|---|---|b3-|---|---|
|-1-|---|---|b3-|---|---|b5-|---|---|bb7|---|---|-1-|

We can cut this up into zones of one sort or another. In previous lessons, we've been looking at shapes based on octave patterns. (A-shape, E-shape, etc.). So below are the 5 shapes along with some voicings in TAB that go along with the shape. All of these are for Fo7. To change to to another o7 chord, we use the same process as for other moveable chords (barre chords, etc.).

Fo7 "E-shape"(root note on the 6th string)

|-1-|---|---|b3-|  
|---|---|bb7|---|
|b3-|---|---|b5-|
|---|---|-1-|---|
|---|b5-|---|---|
|-1-|---|---|b3-|
  1   2   3   4

|--1-1-1-------1-1-1-1--|
|--2-0-2---0---0-0-2-2--|
|--1-1-1-1-1-1-1-1-1-1--|
|--3-0-0-0-0-0-0-0-3-3--|
|--2-2-2-2-----2-----2--|
|--1-1-1-1-1-1----------|

Fo7 "D-shape" (root note on the 4th string)

|---|b3-|---|---|
|bb7|---|---|-1-|
|---|b5-|---|---|
|-1-|---|---|b3-|
|---|---|bb7|---|
|---|b3-|---|---|
  3   4   5   6 

|--4-4-4---4-4--|
|--3-3-6---6-3--|
|--4-4-4-4-4-4--|
|--3-3-3-3---3--|
|----5-5-5-5-5--|
|--------4---4--|

Fo7 "C-shape" (root note on the 5th string)

|---|---|b5-|---|
|---|-1-|---|---|
|---|---|bb7|---|
|---|b3-|---|---|
|bb7|---|---|-1-|
|---|---|b5-|---|
  5   6   7   8

|------7-7-7--|
|--6-6-6-6-6--|
|--7-7-7-7-7--|
|--6-6-6---6--|
|--8-8-8-5----|
|----7---7----|

Fo7 "A-shape" (root note on the 5th string)

|b5-|---|---|bb7|---|
|---|---|b3-|---|---|
|bb7|---|---|-1-|---|
|---|---|b5-|---|---|
|---|-1-|---|---|---|
|b5-|---|---|bb7|---|
  7   8   9  10  11

|--10-10-10--7--7-----------|
|---9--9--9--9--9--9--9--9--|
|--10-10-10--7--7--7-10--7--|
|---9--9--9--9--9--9--9-----|
|---8--8-----8--8--8-----8--|
|------7--------7----10-----|

Fo7 "G-shape" (root note on the 6th string)

|bb7|---|---|-1-|
|---|---|b5-|---|
|-1-|---|---|b3-|
|---|---|bb7|---|
|---|b3-|---|---|
|bb7|---|---|-1-|
 10  11   12  13

|-10-----------|
|-12----12-----|
|-10-10-10-----|
|-12-12-12-12--|
|-11-11-11-11--|
|-10-13----13--|

Look again at the whole fretboard.

|-1-|---|---|b3-|---|---|b5-|---|---|bb7|---|---|--1|
|---|---|bb7|---|---|-1-|---|---|b3-|---|---|b5-|---|
|b3-|---|---|b5-|---|---|bb7|---|---|-1-|---|---|b3-|
|---|---|-1-|---|---|b3-|---|---|b5-|---|---|bb7|---|
|---|b5-|---|---|bb7|---|---|-1-|---|---|b3-|---|---|
|-1-|---|---|b3-|---|---|b5-|---|---|bb7|---|---|-1-|

Notice how the pattern repeats itself through the fretboard. This is due to the diminished seventh chords symmetrical nature. The upside of this is that we can play the same shape at multiple frets on the neck and get the same chord. So one way to look at it is to learn some moveable shapes, and if the root falls on any of the notes played when that shape is played then you are playing the the diminished seventh chord.

Examples:

|---|---|---|
|---|---|---|
|---|-O-|---|
|-O-|---|---|
|---|---|-O-|
|---|-O-|---|
 
|---|---|---|
|---|---|-O-|
|-O-|---|---|
|---|---|-O-|
|---|-O-|---|
|---|---|---|
 
|---|-O-|---|
|-O-|---|---|
|---|-O-|---|
|-O-|---|---|
|---|---|---|
|---|---|---|

Line up any of the above three shapes with the root note that you want and you have the correct o7 chord that you're looking for.

For example, say i want an F#o7 , I take the bottom shape and line up the chord so that the F# on the E-string corresponds to the note on the E-string in the shape, and I have an F#o7chord.

|---|-O-|---|
|-O-|---|---|
|---|-O-|---|
|-O-|---|---|
|---|---|---|
|---|---|---|
  1   2   3 

Ok. So we can make many different voicings out of a given chord (many more than shown here). Choosing for ourselves just what voicing we're going to use to interpret a chord is one part of developing our own style.

INVERSIONS and CHORD SYNONYMS

(Look into inversions (aug 23rds, aug 30ths lessons) and chord synonyms (aug 23) if these ideas are new). We will use Bo7 as our example to be inverted and renamed.

Bo7= B,D,F,Ab (root position, 1 is in the bass)

1rst inversion, 3rd is in the bass
Bo7/D = D,F,Ab,B what D chord is this?
D,F,Ab,B = D,F,Ab,Cb = 1,b3,5,bb7
we could call this Do7.

2nd inversion, 5th is in the bass
Bo7/F= F,Ab,B,D what F chord is this?
F,Ab,B,D = F,Ab,Cb,Ebb = 1,3,b5,bb7
We could call this Fo7

3rd inversion, 7th in the bass.
Bo7/Ab = Ab,B,D,F which Ab chord is this?
Ab,B,D,F = Ab,Cb,Ebb,Gbb = 1,b3,b5,bb7
We could call this Abo7

Due to the Symmetrical nature of the diminished seventh chord, when we invert the chord we end up with the same structure as the original chord although starting on a different root.

To understand this, it helps to see that a diminished seventh chord is created by stacking a minor third on top of a minor third on top of a minor third, and that the diminished seventh which is created by doing this is a minor third below the octave of the root note.

|----------|
|
|----------|
|   O
|-bbO------|
|
|--bO------|
|
|--bO------|

  --O--

Here above is the Co7 chord. C to Eb is a minor third, Eb to Gb is a minor third, and Gb to Bbb is a minor third, and Bbb to C is a minor third.

So for a io7, we could substitute biiio7, bvo7, or vio7 (bbviio7), and vis versa.

CHORDS in CONTEXT

We sometimes see o7 chords written in songs, but there is a way to understand why they pop up where they do? Usually.

Recall, that we harmonized the major scale to get the chords (triads):
I-ii-iii-IV-V-vi-viio (in the key of C: C-Dm-Em-F-G-Am-Bo)
The diminished seventh chord is not found in the major scale or minor scale. Or the melodic minor, or the gypsy minor.

Where do o7 chords turn up in scales?

In the harmonic minor, the o7 shows up as iio7, ivo7, bvio7 and viio7.

There are two scales refered to as the diminished scales. They are modes of each other, they are semi-symmetric, and are refer to as whole-half (W-1/2), and half-whole (1/2-W).

W-1/2 = W-1/2-W-1/2-W-1/2-W-1/2 = 1,2,b3,4,b5,b6,bb7,7
1/2-W = 1/2-W-1/2-W-1/2-W-1/2-W = 1,b2,b3,3,#4/b5,5,6,b7

In the diminished scales a diminished seventh can be built off every step.

So the W-1/2 can be played over: io7, iio7, biiio7, ivo7, bvo7, bvio7, and viio7.

And the 1/2-W can be played over io7, biio7, biiio7, iiio7, #ivo7, bvo7, vo7, vio7, and bviio7.

The diminished seventh can also be found in the hungarian scale and it's modes.
hungarian = m3-1/2-W-1/2-W-1/2-W = 1,b3,3,#4,5,6,b7 (and root note on C =C,D#,E,F#,G,A,Bb).
The hungarian scale contains the following o7 chords:
io7, #iio7, biiio7, #ivo7, bvo7, vio7

So let's consider some progressions.

Diminished Seventh chords are often heard as passing chords, that is they are created as temporary chords while moving from one chord to another, in a series of chords.

In Bossa Nova, #io7 is sometimes used as a substitute for V7 (C#o7 in place of C7).

Since the dim7 chord is symmetrical, we could also substitute other dim7 chords in place of 7 chord. We could replace I7 with #io7, iiio7, vo7, bviio7.

Sometimes for dramatic effect we hear different inversions of the o7 chord played in succession. Such as io7-biiio7-bvo7-biiio7.

|------------|
|--6-9-12-9--|
|--4-7-10-7--|
|--6-9-12-9--|
|--5-8-11-8--|
|------------|

(something similar can be heard in the Beatles "Michelle", which has a solo with one of the diminished scales BTW)

Although extensions are sometimes found on the dim7 chord, most usually they are not, so i've not listed any. The intermediate/advanced student can create his own by filling in other intervals (such as 2nds, 4ths, and 6ths).

Next lesson is on the Dominant ninth chord (dom9, 9).

Peace,
Christopher Roberts
snglstringtheory@aol.com


How do I change all those numbers to letters (for notes, chords, etc.)? Here's a transposition chart simianmoon.com/snglstringtheory/guitar/8theory3.html

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Previous Lesson - Minor/major 7 Chords

Last updated October 3, 2002
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