Why does Cdim7 contain an A instead of a Bb?

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CM7 - C, E, G, B

C7 - C, E, G, Bb

Cm7 - C, Eb, G, Bb

Caug7 - C, E, G#, Bb

But...

Cdim7 - C, Eb, Gb, A.

Why Does Cdim7 contain an A and not a Bb?

theory chords chord-theory harmony

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edited 1 hour ago

Richard

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Alex G-I

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• 
  
  
  

  
  

  
  
  
  
  
  

  
  The other answerers have already addressed the question more than adequately so I won't duplicate them, but I will just point out additionally that there does exist a chord "C Eb Gb Bb" and that it's called the "half diminished" chord, because it has a diminished five but a non-diminished 7th. It's often written as Cø and is also a useful chord (it's really pretty).
  – Some_Guy
  17 mins ago
  

  
  
  
  

add a comment | 

up vote
3
down vote

favorite

CM7 - C, E, G, B

C7 - C, E, G, Bb

Cm7 - C, Eb, G, Bb

Caug7 - C, E, G#, Bb

But...

Cdim7 - C, Eb, Gb, A.

Why Does Cdim7 contain an A and not a Bb?

theory chords chord-theory harmony

share|improve this question

edited 1 hour ago

Richard

32.9k671138

asked 2 hours ago

Alex G-I

142

New contributor

Alex G-I is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  The other answerers have already addressed the question more than adequately so I won't duplicate them, but I will just point out additionally that there does exist a chord "C Eb Gb Bb" and that it's called the "half diminished" chord, because it has a diminished five but a non-diminished 7th. It's often written as Cø and is also a useful chord (it's really pretty).
  – Some_Guy
  17 mins ago
  

  
  
  
  

add a comment | 

up vote
3
down vote

favorite

up vote
3
down vote

favorite

CM7 - C, E, G, B

C7 - C, E, G, Bb

Cm7 - C, Eb, G, Bb

Caug7 - C, E, G#, Bb

But...

Cdim7 - C, Eb, Gb, A.

Why Does Cdim7 contain an A and not a Bb?

theory chords chord-theory harmony

share|improve this question

edited 1 hour ago

Richard

32.9k671138

asked 2 hours ago

Alex G-I

142

New contributor

Alex G-I is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

CM7 - C, E, G, B

C7 - C, E, G, Bb

Cm7 - C, Eb, G, Bb

Caug7 - C, E, G#, Bb

But...

Cdim7 - C, Eb, Gb, A.

Why Does Cdim7 contain an A and not a Bb?

theory chords chord-theory harmony

theory chords chord-theory harmony

share|improve this question

edited 1 hour ago

Richard

32.9k671138

asked 2 hours ago

Alex G-I

142

New contributor

Alex G-I is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited 1 hour ago

Richard

32.9k671138

asked 2 hours ago

Alex G-I

142

New contributor

Alex G-I is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

share|improve this question

edited 1 hour ago

Richard

32.9k671138

edited 1 hour ago

Richard

32.9k671138

edited 1 hour ago

Richard

32.9k671138

32.9k671138

asked 2 hours ago

Alex G-I

142

New contributor

Alex G-I is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 2 hours ago

Alex G-I

142

asked 2 hours ago

Alex G-I

142

142

New contributor

Alex G-I is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

New contributor

Alex G-I is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

Alex G-I is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  The other answerers have already addressed the question more than adequately so I won't duplicate them, but I will just point out additionally that there does exist a chord "C Eb Gb Bb" and that it's called the "half diminished" chord, because it has a diminished five but a non-diminished 7th. It's often written as Cø and is also a useful chord (it's really pretty).
  – Some_Guy
  17 mins ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  The other answerers have already addressed the question more than adequately so I won't duplicate them, but I will just point out additionally that there does exist a chord "C Eb Gb Bb" and that it's called the "half diminished" chord, because it has a diminished five but a non-diminished 7th. It's often written as Cø and is also a useful chord (it's really pretty).
  – Some_Guy
  17 mins ago
  

  
  
  
  

The other answerers have already addressed the question more than adequately so I won't duplicate them, but I will just point out additionally that there does exist a chord "C Eb Gb Bb" and that it's called the "half diminished" chord, because it has a diminished five but a non-diminished 7th. It's often written as Cø and is also a useful chord (it's really pretty).
– Some_Guy
17 mins ago

The other answerers have already addressed the question more than adequately so I won't duplicate them, but I will just point out additionally that there does exist a chord "C Eb Gb Bb" and that it's called the "half diminished" chord, because it has a diminished five but a non-diminished 7th. It's often written as Cø and is also a useful chord (it's really pretty).
– Some_Guy
17 mins ago

add a comment | 

4 Answers
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up vote
2
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A Cdim7 chord is actually spelled C-Eb-Gb-Bbb, where the interval from C to Bbb is called a diminished seventh. The interval from C to A is a major sixth, but sometimes you do see people spell Cdim7 as C-Eb-Gb-A for convenience to avoid the double flat, it is just technically incorrect. This chord is sometimes called a fully-diminished chord, in contrast to a half-diminished chord. A half-diminished C chord (Cmin7b5, C-7b5, or C^{∅}) is spelled: C-Eb-Gb-Bb. These are often found in ii-V-i progressions in jazz.

share|improve this answer

answered 2 hours ago

David Bowling

3,61611030

• 
  
  
  

  
  

  
  
  
  
  
  

  
  C-E♭-G♭-A is also the correct spelling of the pitches in Adim7. And it's OK to put the C (or indeed E♭ or G♭) in the bass.
  – Rosie F
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @RosieF -- not sure I understand your point; Adim7 and Cdim7 are enharmonically spelled the same way, but are not the same chords.
  – David Bowling
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Indeed. I just didn't want anyone reading your answer to think the spelling with an A is as you say "technically incorrect". A composer may write an A and yet be technically correct. It's just that the technically correct chord symbol would then be Adim7. When it comes to deciding how to spell a dim7 chord, let voice leading be your guide. And yes, perhaps simplify for convenience if you feel that's right. The chord symbol comes later. The music determines the chord symbol, not the other way around. The composer needn't let the symbol determine the spelling.
  – Rosie F
  1 hour ago
  

  
  
  
  

add a comment | 

up vote
2
down vote

Other answers have pointed out that it's a B♭♭, not an A. To answer the question "why not a B♭":

The chord in question is the chord of the diminished 7th. As David Bowling and Richard have stated, if the root is C, the diminished 7th is B♭♭.

The chord is also called the "diminished 7th chord". This name and its chord symbol Cdim7 are perhaps confusing. I don't know if this is what you thought, but, just for the record, "Cdim7" does not mean

• the diminished triad C-E♭-G♭ as indicated by "Cdim"


• the pitch B♭ as indicated by "7", just as C7 means a C triad plus B♭

It's not a [ diminished triad ] with a seventh. It's a chord of the [ diminished seventh ].

share|improve this answer

answered 1 hour ago

Rosie F

1,021211

add a comment | 

up vote
1
down vote

It actually contains a Bbb (double flat). Often (mis)spelt as A for convenience. You'll also often see it notated as C, Eb, F#, A.

A dim7 chord is a pile of minor 3rds. A minor 3rd up from Gb is Bbb.

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answered 2 hours ago

Laurence Payne

28.3k1351

add a comment | 

up vote
1
down vote

C°7 actually includes a B doubleflat.

A major seventh above C is B and a minor seventh above C is B♭. This means that a diminished seventh above C is actually B♭♭, which is enharmonic to A.

But the seventh is not A, because A is just a sixth above C. A is enharmonic to B♭♭, but since we want the seventh above C, it must be B♭♭, not A.

But it gets more interesting: since fully diminished sevenths are just stacked minor thirds, they can be spelled four different ways, with each pitch as root; we say that these chords are enharmonic, just like we say that A is enharmonic to B♭♭.

This then means that C–E♭–G♭–A is a diminished seventh chord, but with A as the root: A–C–E♭–G♭. If E♭ is the root, we'd rather spell it as D♯–F♯–A–C. If G♭ is the root, we'd spell it as F♯–A–C–E♭.

These chords all sound the same as C°7, but they are spelled differently.

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edited 2 hours ago

answered 2 hours ago

Richard

32.9k671138

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4 Answers
4

active

oldest

votes

4 Answers
4

active

oldest

votes

active

oldest

votes

active

oldest

votes

up vote
2
down vote

A Cdim7 chord is actually spelled C-Eb-Gb-Bbb, where the interval from C to Bbb is called a diminished seventh. The interval from C to A is a major sixth, but sometimes you do see people spell Cdim7 as C-Eb-Gb-A for convenience to avoid the double flat, it is just technically incorrect. This chord is sometimes called a fully-diminished chord, in contrast to a half-diminished chord. A half-diminished C chord (Cmin7b5, C-7b5, or C^{∅}) is spelled: C-Eb-Gb-Bb. These are often found in ii-V-i progressions in jazz.

share|improve this answer

answered 2 hours ago

David Bowling

3,61611030

• 
  
  
  

  
  

  
  
  
  
  
  

  
  C-E♭-G♭-A is also the correct spelling of the pitches in Adim7. And it's OK to put the C (or indeed E♭ or G♭) in the bass.
  – Rosie F
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @RosieF -- not sure I understand your point; Adim7 and Cdim7 are enharmonically spelled the same way, but are not the same chords.
  – David Bowling
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Indeed. I just didn't want anyone reading your answer to think the spelling with an A is as you say "technically incorrect". A composer may write an A and yet be technically correct. It's just that the technically correct chord symbol would then be Adim7. When it comes to deciding how to spell a dim7 chord, let voice leading be your guide. And yes, perhaps simplify for convenience if you feel that's right. The chord symbol comes later. The music determines the chord symbol, not the other way around. The composer needn't let the symbol determine the spelling.
  – Rosie F
  1 hour ago
  

  
  
  
  

add a comment | 

up vote
2
down vote

A Cdim7 chord is actually spelled C-Eb-Gb-Bbb, where the interval from C to Bbb is called a diminished seventh. The interval from C to A is a major sixth, but sometimes you do see people spell Cdim7 as C-Eb-Gb-A for convenience to avoid the double flat, it is just technically incorrect. This chord is sometimes called a fully-diminished chord, in contrast to a half-diminished chord. A half-diminished C chord (Cmin7b5, C-7b5, or C^{∅}) is spelled: C-Eb-Gb-Bb. These are often found in ii-V-i progressions in jazz.

share|improve this answer

answered 2 hours ago

David Bowling

3,61611030

• 
  
  
  

  
  

  
  
  
  
  
  

  
  C-E♭-G♭-A is also the correct spelling of the pitches in Adim7. And it's OK to put the C (or indeed E♭ or G♭) in the bass.
  – Rosie F
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @RosieF -- not sure I understand your point; Adim7 and Cdim7 are enharmonically spelled the same way, but are not the same chords.
  – David Bowling
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Indeed. I just didn't want anyone reading your answer to think the spelling with an A is as you say "technically incorrect". A composer may write an A and yet be technically correct. It's just that the technically correct chord symbol would then be Adim7. When it comes to deciding how to spell a dim7 chord, let voice leading be your guide. And yes, perhaps simplify for convenience if you feel that's right. The chord symbol comes later. The music determines the chord symbol, not the other way around. The composer needn't let the symbol determine the spelling.
  – Rosie F
  1 hour ago
  

  
  
  
  

add a comment | 

up vote
2
down vote

up vote
2
down vote

A Cdim7 chord is actually spelled C-Eb-Gb-Bbb, where the interval from C to Bbb is called a diminished seventh. The interval from C to A is a major sixth, but sometimes you do see people spell Cdim7 as C-Eb-Gb-A for convenience to avoid the double flat, it is just technically incorrect. This chord is sometimes called a fully-diminished chord, in contrast to a half-diminished chord. A half-diminished C chord (Cmin7b5, C-7b5, or C^{∅}) is spelled: C-Eb-Gb-Bb. These are often found in ii-V-i progressions in jazz.

share|improve this answer

answered 2 hours ago

David Bowling

3,61611030

A Cdim7 chord is actually spelled C-Eb-Gb-Bbb, where the interval from C to Bbb is called a diminished seventh. The interval from C to A is a major sixth, but sometimes you do see people spell Cdim7 as C-Eb-Gb-A for convenience to avoid the double flat, it is just technically incorrect. This chord is sometimes called a fully-diminished chord, in contrast to a half-diminished chord. A half-diminished C chord (Cmin7b5, C-7b5, or C^{∅}) is spelled: C-Eb-Gb-Bb. These are often found in ii-V-i progressions in jazz.

share|improve this answer

answered 2 hours ago

David Bowling

3,61611030

share|improve this answer

share|improve this answer

answered 2 hours ago

David Bowling

3,61611030

answered 2 hours ago

David Bowling

3,61611030

answered 2 hours ago

David Bowling

3,61611030

3,61611030

• 
  
  
  

  
  

  
  
  
  
  
  

  
  C-E♭-G♭-A is also the correct spelling of the pitches in Adim7. And it's OK to put the C (or indeed E♭ or G♭) in the bass.
  – Rosie F
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @RosieF -- not sure I understand your point; Adim7 and Cdim7 are enharmonically spelled the same way, but are not the same chords.
  – David Bowling
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Indeed. I just didn't want anyone reading your answer to think the spelling with an A is as you say "technically incorrect". A composer may write an A and yet be technically correct. It's just that the technically correct chord symbol would then be Adim7. When it comes to deciding how to spell a dim7 chord, let voice leading be your guide. And yes, perhaps simplify for convenience if you feel that's right. The chord symbol comes later. The music determines the chord symbol, not the other way around. The composer needn't let the symbol determine the spelling.
  – Rosie F
  1 hour ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  C-E♭-G♭-A is also the correct spelling of the pitches in Adim7. And it's OK to put the C (or indeed E♭ or G♭) in the bass.
  – Rosie F
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @RosieF -- not sure I understand your point; Adim7 and Cdim7 are enharmonically spelled the same way, but are not the same chords.
  – David Bowling
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Indeed. I just didn't want anyone reading your answer to think the spelling with an A is as you say "technically incorrect". A composer may write an A and yet be technically correct. It's just that the technically correct chord symbol would then be Adim7. When it comes to deciding how to spell a dim7 chord, let voice leading be your guide. And yes, perhaps simplify for convenience if you feel that's right. The chord symbol comes later. The music determines the chord symbol, not the other way around. The composer needn't let the symbol determine the spelling.
  – Rosie F
  1 hour ago
  

  
  
  
  

C-E♭-G♭-A is also the correct spelling of the pitches in Adim7. And it's OK to put the C (or indeed E♭ or G♭) in the bass.
– Rosie F
1 hour ago

C-E♭-G♭-A is also the correct spelling of the pitches in Adim7. And it's OK to put the C (or indeed E♭ or G♭) in the bass.
– Rosie F
1 hour ago

@RosieF -- not sure I understand your point; Adim7 and Cdim7 are enharmonically spelled the same way, but are not the same chords.
– David Bowling
1 hour ago

@RosieF -- not sure I understand your point; Adim7 and Cdim7 are enharmonically spelled the same way, but are not the same chords.
– David Bowling
1 hour ago

Indeed. I just didn't want anyone reading your answer to think the spelling with an A is as you say "technically incorrect". A composer may write an A and yet be technically correct. It's just that the technically correct chord symbol would then be Adim7. When it comes to deciding how to spell a dim7 chord, let voice leading be your guide. And yes, perhaps simplify for convenience if you feel that's right. The chord symbol comes later. The music determines the chord symbol, not the other way around. The composer needn't let the symbol determine the spelling.
– Rosie F
1 hour ago

Indeed. I just didn't want anyone reading your answer to think the spelling with an A is as you say "technically incorrect". A composer may write an A and yet be technically correct. It's just that the technically correct chord symbol would then be Adim7. When it comes to deciding how to spell a dim7 chord, let voice leading be your guide. And yes, perhaps simplify for convenience if you feel that's right. The chord symbol comes later. The music determines the chord symbol, not the other way around. The composer needn't let the symbol determine the spelling.
– Rosie F
1 hour ago

add a comment | 

up vote
2
down vote

Other answers have pointed out that it's a B♭♭, not an A. To answer the question "why not a B♭":

The chord in question is the chord of the diminished 7th. As David Bowling and Richard have stated, if the root is C, the diminished 7th is B♭♭.

The chord is also called the "diminished 7th chord". This name and its chord symbol Cdim7 are perhaps confusing. I don't know if this is what you thought, but, just for the record, "Cdim7" does not mean

• the diminished triad C-E♭-G♭ as indicated by "Cdim"


• the pitch B♭ as indicated by "7", just as C7 means a C triad plus B♭

It's not a [ diminished triad ] with a seventh. It's a chord of the [ diminished seventh ].

share|improve this answer

answered 1 hour ago

Rosie F

1,021211

add a comment | 

up vote
2
down vote

Other answers have pointed out that it's a B♭♭, not an A. To answer the question "why not a B♭":

The chord in question is the chord of the diminished 7th. As David Bowling and Richard have stated, if the root is C, the diminished 7th is B♭♭.

The chord is also called the "diminished 7th chord". This name and its chord symbol Cdim7 are perhaps confusing. I don't know if this is what you thought, but, just for the record, "Cdim7" does not mean

• the diminished triad C-E♭-G♭ as indicated by "Cdim"


• the pitch B♭ as indicated by "7", just as C7 means a C triad plus B♭

It's not a [ diminished triad ] with a seventh. It's a chord of the [ diminished seventh ].

share|improve this answer

answered 1 hour ago

Rosie F

1,021211

add a comment | 

up vote
2
down vote

up vote
2
down vote

Other answers have pointed out that it's a B♭♭, not an A. To answer the question "why not a B♭":

The chord in question is the chord of the diminished 7th. As David Bowling and Richard have stated, if the root is C, the diminished 7th is B♭♭.

The chord is also called the "diminished 7th chord". This name and its chord symbol Cdim7 are perhaps confusing. I don't know if this is what you thought, but, just for the record, "Cdim7" does not mean

• the diminished triad C-E♭-G♭ as indicated by "Cdim"


• the pitch B♭ as indicated by "7", just as C7 means a C triad plus B♭

It's not a [ diminished triad ] with a seventh. It's a chord of the [ diminished seventh ].

share|improve this answer

answered 1 hour ago

Rosie F

1,021211

Other answers have pointed out that it's a B♭♭, not an A. To answer the question "why not a B♭":

The chord in question is the chord of the diminished 7th. As David Bowling and Richard have stated, if the root is C, the diminished 7th is B♭♭.

The chord is also called the "diminished 7th chord". This name and its chord symbol Cdim7 are perhaps confusing. I don't know if this is what you thought, but, just for the record, "Cdim7" does not mean

• the diminished triad C-E♭-G♭ as indicated by "Cdim"


• the pitch B♭ as indicated by "7", just as C7 means a C triad plus B♭

It's not a [ diminished triad ] with a seventh. It's a chord of the [ diminished seventh ].

share|improve this answer

answered 1 hour ago

Rosie F

1,021211

share|improve this answer

share|improve this answer

answered 1 hour ago

Rosie F

1,021211

answered 1 hour ago

Rosie F

1,021211

answered 1 hour ago

Rosie F

1,021211

1,021211

add a comment | 

add a comment | 

up vote
1
down vote

It actually contains a Bbb (double flat). Often (mis)spelt as A for convenience. You'll also often see it notated as C, Eb, F#, A.

A dim7 chord is a pile of minor 3rds. A minor 3rd up from Gb is Bbb.

share|improve this answer

answered 2 hours ago

Laurence Payne

28.3k1351

add a comment | 

up vote
1
down vote

It actually contains a Bbb (double flat). Often (mis)spelt as A for convenience. You'll also often see it notated as C, Eb, F#, A.

A dim7 chord is a pile of minor 3rds. A minor 3rd up from Gb is Bbb.

share|improve this answer

answered 2 hours ago

Laurence Payne

28.3k1351

add a comment | 

up vote
1
down vote

up vote
1
down vote

It actually contains a Bbb (double flat). Often (mis)spelt as A for convenience. You'll also often see it notated as C, Eb, F#, A.

A dim7 chord is a pile of minor 3rds. A minor 3rd up from Gb is Bbb.

share|improve this answer

answered 2 hours ago

Laurence Payne

28.3k1351

It actually contains a Bbb (double flat). Often (mis)spelt as A for convenience. You'll also often see it notated as C, Eb, F#, A.

A dim7 chord is a pile of minor 3rds. A minor 3rd up from Gb is Bbb.

share|improve this answer

answered 2 hours ago

Laurence Payne

28.3k1351

share|improve this answer

share|improve this answer

answered 2 hours ago

Laurence Payne

28.3k1351

answered 2 hours ago

Laurence Payne

28.3k1351

answered 2 hours ago

Laurence Payne

28.3k1351

28.3k1351

add a comment | 

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up vote
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C°7 actually includes a B doubleflat.

A major seventh above C is B and a minor seventh above C is B♭. This means that a diminished seventh above C is actually B♭♭, which is enharmonic to A.

But the seventh is not A, because A is just a sixth above C. A is enharmonic to B♭♭, but since we want the seventh above C, it must be B♭♭, not A.

But it gets more interesting: since fully diminished sevenths are just stacked minor thirds, they can be spelled four different ways, with each pitch as root; we say that these chords are enharmonic, just like we say that A is enharmonic to B♭♭.

This then means that C–E♭–G♭–A is a diminished seventh chord, but with A as the root: A–C–E♭–G♭. If E♭ is the root, we'd rather spell it as D♯–F♯–A–C. If G♭ is the root, we'd spell it as F♯–A–C–E♭.

These chords all sound the same as C°7, but they are spelled differently.

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edited 2 hours ago

answered 2 hours ago

Richard

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up vote
1
down vote

C°7 actually includes a B doubleflat.

A major seventh above C is B and a minor seventh above C is B♭. This means that a diminished seventh above C is actually B♭♭, which is enharmonic to A.

But the seventh is not A, because A is just a sixth above C. A is enharmonic to B♭♭, but since we want the seventh above C, it must be B♭♭, not A.

But it gets more interesting: since fully diminished sevenths are just stacked minor thirds, they can be spelled four different ways, with each pitch as root; we say that these chords are enharmonic, just like we say that A is enharmonic to B♭♭.

This then means that C–E♭–G♭–A is a diminished seventh chord, but with A as the root: A–C–E♭–G♭. If E♭ is the root, we'd rather spell it as D♯–F♯–A–C. If G♭ is the root, we'd spell it as F♯–A–C–E♭.

These chords all sound the same as C°7, but they are spelled differently.

share|improve this answer

edited 2 hours ago

answered 2 hours ago

Richard

32.9k671138

add a comment | 

up vote
1
down vote

up vote
1
down vote

C°7 actually includes a B doubleflat.

A major seventh above C is B and a minor seventh above C is B♭. This means that a diminished seventh above C is actually B♭♭, which is enharmonic to A.

But the seventh is not A, because A is just a sixth above C. A is enharmonic to B♭♭, but since we want the seventh above C, it must be B♭♭, not A.

But it gets more interesting: since fully diminished sevenths are just stacked minor thirds, they can be spelled four different ways, with each pitch as root; we say that these chords are enharmonic, just like we say that A is enharmonic to B♭♭.

This then means that C–E♭–G♭–A is a diminished seventh chord, but with A as the root: A–C–E♭–G♭. If E♭ is the root, we'd rather spell it as D♯–F♯–A–C. If G♭ is the root, we'd spell it as F♯–A–C–E♭.

These chords all sound the same as C°7, but they are spelled differently.

share|improve this answer

edited 2 hours ago

answered 2 hours ago

Richard

32.9k671138

C°7 actually includes a B doubleflat.

A major seventh above C is B and a minor seventh above C is B♭. This means that a diminished seventh above C is actually B♭♭, which is enharmonic to A.

But the seventh is not A, because A is just a sixth above C. A is enharmonic to B♭♭, but since we want the seventh above C, it must be B♭♭, not A.

But it gets more interesting: since fully diminished sevenths are just stacked minor thirds, they can be spelled four different ways, with each pitch as root; we say that these chords are enharmonic, just like we say that A is enharmonic to B♭♭.

This then means that C–E♭–G♭–A is a diminished seventh chord, but with A as the root: A–C–E♭–G♭. If E♭ is the root, we'd rather spell it as D♯–F♯–A–C. If G♭ is the root, we'd spell it as F♯–A–C–E♭.

These chords all sound the same as C°7, but they are spelled differently.

share|improve this answer

edited 2 hours ago

answered 2 hours ago

Richard

32.9k671138

share|improve this answer

share|improve this answer

edited 2 hours ago

edited 2 hours ago

edited 2 hours ago

answered 2 hours ago

Richard

32.9k671138

answered 2 hours ago

Richard

32.9k671138

answered 2 hours ago

Richard

32.9k671138

32.9k671138

add a comment | 

add a comment | 

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