Fully Diminished chords

[bjenkins24]

I haven't taken theory for a while now and I can't seem to remember how to analyze a fully diminished chord.  For example, in Beethoven's Sonata Op.31 No.3 1st movement it starts out with a ii65 in Eb then goes to some kind of fully diminshed chord?  A?  But what would I use in a harmonic analysis to write that that's what the chord is...  Sorry if my question doesn't make a whole lot of sense, I'm trying to do a harmonic analysis on many of the pieces I play in order to understand the piece better and I've ran into this problem a lot, I can't remember how one would analyze fully diminshed chords, because they don't seem to be notes in any scale.  For example no key has A, C, Eb, and Gb as part of the key signature because A would be flat before the G would be.  Also it seems to me that if you invert a fully diminished chord then the root can just change if you change the spelling of the chord.  So how do you know what the root is?  Is it just by the way it's spelled in the context?

I'm just confused.  Anyone wanna chime in with some help?

[Bob]

They could be pointing to something.  viio resolving a half step up.  Something like that.  And if it's to a secondary dominant, it can look pretty chromatic.

I don't think all the notes are going to be in the key, unless it's the viio.

Look at how they function, where they go.  That will tell you what it is.  Although it could be spelled differently for the performer's convenience.

[bjenkins24]

But would I just write viio7 then?  Or to use the Eb sonata op.31 no.3 as an example.  It is in Eb and the first chord is obviously a ii65 followed by from the bottom up: A, Eb, C, Eb, Gb then another measure of the chord followed by a I64 then V.  Now the 2nd chord isn't vii although I guess it could be viio7 of V.  Would that be right? 

The big thing that is confusing me that even in Bb(the dominant of Eb) G is not flat so how could you just right viio7 of V when the Gb isn't in the key...  You get where I'm coming from here?
for example in major the chords go something like this right?
I ii iii IV V vi viio
for sake of argument we'll use C major as the key, if we add 7ths to those chords then we have
C,E,G,B (Major 7th chord), D,F,A,C (minor 7th chord), E,G,B,D (minor 7th), F,A,C,E (major 7th), G,B,D,F (dominant 7th), A,C,E,G (minor 7th), B,D,F,A (half diminished 7th).  Now if I wanted a C dominant 7th chord (with the Bb) I couldn't just write I7 because that would be the major 7th chord because Bb isn't in the key of C.  So I would have to take the dominant 7th chord from the key of F so it would be V7/IV and kabam I have a note not in the key of C. 

Now my question is how in the world do I get a fully diminished 7th chord?  Because it doesn't seem to exist in any key.  As far as I can see, in the minor mode we have the same problem.  So even though it's not in the key do I just analyze the fully diminished chords as viio of whatever makes sense?  Is it an exception to the rule like the german/italian/french 6ths and the neapolitan chord?  Sorry if I'm not making any sense I don't know how to explain my question well.  I asked my friend and it took me like 20 minutes plus being at a piano to explain what the heck my question was 

Ok, hope someone can help!

[Bob]

Hmm.... I don't have the piece in front of me.

ii65 -- Could be ii V I with a I64 thrown in.

There could be voice leading resulting in the ii65.


I believe you can have passing viio7's or something like that.  Non-functional ones.

You can borrow from the relative minor.  iio then.

The second scale step might be the important thing though, regardless of what's on top of it.


I'm still not quite following.  They don't have to stick with notes in the key.  If Beethoven wants a viio7, then he can use one.  Doesn't matter if the notes are in the key or not.


Are you asking where a fully dimished chord comes from in the first place, considering the scale gives us a half-dim chord on the seventh step if you build thirds?
I do remember having that come up in a theory class.  I don't remember the reply.  I think it may have been because making the 7th a half step lower made it that much more powerful a pull for the resolution.  Maybe the answer is -- because it sounds better?  or sounds right?

Interest question.  One of those holes in theory land.  Makes me wonder what else is really out there then.

My answer would be the pull to the resolution is strengthened, it sounds better to have stacked m3's rather than having one M3 thrown in, and it could be a dissonance thing then. 

You've also got a m7 interval in the chord, which might suggest a dominant function.  Say on a C... C Eb Gb Bb... That starts looking like a domainant chord with lowered third and fifth.  Which is another way to think of half-dim's anyway.

Or... You've got more options for modulation with the chord being so symetrical.  What chord is it?  Who knows?  There are four different chords it might be, and four different directions to resolve it.  So if you want to modulate around, that could be a useful chord.  As opposed to getting locked into it only being used one way.


I'm curious about other replies.

[jlh]

But would I just write viio7 then?  Or to use the Eb sonata op.31 no.3 as an example.  It is in Eb and the first chord is obviously a ii65 followed by from the bottom up: A, Eb, C, Eb, Gb then another measure of the chord followed by a I64 then V.  Now the 2nd chord isn't vii although I guess it could be viio7 of V.  Would that be right? 

The big thing that is confusing me that even in Bb(the dominant of Eb) G is not flat so how could you just right viio7 of V when the Gb isn't in the key...  You get where I'm coming from here?
for example in major the chords go something like this right?
I ii iii IV V vi viio
for sake of argument we'll use C major as the key, if we add 7ths to those chords then we have
C,E,G,B (Major 7th chord), D,F,A,C (minor 7th chord), E,G,B,D (minor 7th), F,A,C,E (major 7th), G,B,D,F (dominant 7th), A,C,E,G (minor 7th), B,D,F,A (half diminished 7th).  Now if I wanted a C dominant 7th chord (with the Bb) I couldn't just write I7 because that would be the major 7th chord because Bb isn't in the key of C.  So I would have to take the dominant 7th chord from the key of F so it would be V7/IV and kabam I have a note not in the key of C. 

Now my question is how in the world do I get a fully diminished 7th chord?  Because it doesn't seem to exist in any key.  As far as I can see, in the minor mode we have the same problem.  So even though it's not in the key do I just analyze the fully diminished chords as viio of whatever makes sense?  Is it an exception to the rule like the german/italian/french 6ths and the neapolitan chord?  Sorry if I'm not making any sense I don't know how to explain my question well.  I asked my friend and it took me like 20 minutes plus being at a piano to explain what the heck my question was 

Ok, hope someone can help!

You're quite right about everything... though you haven't considered the 1 option that makes the most sense. 

This is an example of a common-tone diminished 7th chord (ct^o7), which is a fully diminished 7th chord that embellishes in a linear fashion another chord with which it shares 1 note.  This other chord is most often the I chord, the tonic triad, and the shared pitch is most commonly the tonic pitch, the root of the triad.  It is a chromatic chord in the key, which means that some of the notes come from outside the key.  The ct⁰⁷ does not function as a leading-tone diminished-7th chord, that is, it does not "resolve" to its own tonic, as do most diminished-7th chords that function as vii⁰⁷, in which the leading tone, upon which the chord is constructed, moves to the tonic.  The vii^o7 has no notes in common with the chord to which it resolves, whereas the ct^o7 shares 1 pitch with the chord it embellishes.

Technically, the Gb should be an F# in this context, but then again, ct^o7 chords do not typically resolve to a V or I 6/4 either.  Your guess is as good as mine why Beethoven wrote it this way, but obviously the function of the chord in question is not that of vii^o7/V but rather that of a ct^o7.

Hope this helps!

Josh

[pinksynth]

Lest we forget, harmonic minor contains a fully diminished tetrad.

[schartmanovich]

I haven't taken theory for a while now and I can't seem to remember how to analyze a fully diminished chord.  For example, in Beethoven's Sonata Op.31 No.3 1st movement it starts out with a ii65 in Eb then goes to some kind of fully diminshed chord?  A?  But what would I use in a harmonic analysis to write that that's what the chord is...  Sorry if my question doesn't make a whole lot of sense, I'm trying to do a harmonic analysis on many of the pieces I play in order to understand the piece better and I've ran into this problem a lot, I can't remember how one would analyze fully diminshed chords, because they don't seem to be notes in any scale.  For example no key has A, C, Eb, and Gb as part of the key signature because A would be flat before the G would be.  Also it seems to me that if you invert a fully diminished chord then the root can just change if you change the spelling of the chord.  So how do you know what the root is?  Is it just by the way it's spelled in the context?

I'm just confused.  Anyone wanna chime in with some help?

The progression is as follows:

ii65 -  vii07 OF V - V64 (cadential 64 on the fermata) - V7 - I

[daniloperusina]

I think the diminished chord in the Beethoven example should be analysed as a F7/A with flattened 9th (Gb) and without the root (F)
So, it's the dominant of the dominant.

Usually, the function, and therefore the spelling, of a diminished chord can be found in that way. Like it's a dominant chord in "disguise". The root-note will not be included, but the 3rd, 5th, 7th & b9 will.

The chord progression in Op 31:3 would be
Fm7/Ab - F7b9(without root)/A - Bb64 - Bb7

[ramseytheii]

I think the diminished chord in the Beethoven example should be analysed as a F7/A with flattened 9th (Gb) and without the root (F)
So, it's the dominant of the dominant.

Usually, the function, and therefore the spelling, of a diminished chord can be found in that way. Like it's a dominant chord in "disguise". The root-note will not be included, but the 3rd, 5th, 7th & b9 will.

The chord progression in Op 31:3 would be
Fm7/Ab - F7b9(without root)/A - Bb64 - Bb7

Excellent post!

Walter Ramsey

[schartmanovich]

I think the diminished chord in the Beethoven example should be analysed as a F7/A with flattened 9th (Gb) and without the root (F)
So, it's the dominant of the dominant.

Usually, the function, and therefore the spelling, of a diminished chord can be found in that way. Like it's a dominant chord in "disguise". The root-note will not be included, but the 3rd, 5th, 7th & b9 will.

The chord progression in Op 31:3 would be
Fm7/Ab - F7b9(without root)/A - Bb64 - Bb7

What is the use in analyzing a passage based on what is not there rather than what is? I think you're simply picking up on the fact that there is only a semitone's difference between a viio7 and a V7 chord. Since Beethoven clearly gives the vii07 version here, there is no sense in analyzing a V7 without its root. In addition, my original analysis preserves the concatenation of harmonic functions that is never violated in this music; in this case, pre-dominant (II6/5 - viio7 of V) - dominant (cadential 6/4 - V7) - tonic (I).

[pianoplayjl]

isn't the notes in a dimished chord separated a minor third apart?