Hi,

I'm getting a little confused with diminished 7th's and have a few questions.

1. Does a diminished 7th chord only resolve on to chord 1 and if so can it be any inversion?

2. if you are in E major and writing a dim. 7th on D#, would you write the C# as a C natural or C flat?

3. Finally (for now) if you see the words 'diminished 7th' does that mean the chord built on the 7th degree of the scale with an added 7th....what about a dim.ii chord with added 7th ?

I'm not sure where this comes in exam terms, but if you're not talking about specific exam criteria, dim 7th are wonderous beasts, as you can use them to do a handbrake turn in harmonic terms - they'll resolve almost anywhere, so are great for modulating into remote or close keys - one of the best ways to find out how many things you can do with them is to sit at a piano and see how many different satisfactory resolutions you can find ... you can treat any note of the chord as a leading note and it'll work. One standard progression would be to resolve it onto a Ic V I cadence, e.g. F#dim7 | C/E | G7 | C.

2. A diminished 7th above D# is C, (D# to Cx is a maj 7th, D# to C# a min 7th, D# to C a dim 7th.)

3. A diminished 7th can happen on any degree of the scale - the term is only referring to the spelling of the chord.

Thanks for your reply, I realise that D# to C is a dim 7th , but how would you spell it in the key of E major as there is a c# in the key signature, would it be a C natural or would I write a C flat to flatten the # in the key signature?

Put a natural sign in front of the C, as that lowers ('flattens') the 7th degree of the scale by a semitone. (Interestingly, in the 17th century, they did use flats and sharps to raise/lower/naturalise notes, rather than natural signs.)

Perhaps a more thorough grounding in the basics of notation would be useful before wondering where diminished sevenths resolve to? It would help with the understanding of your other questions too.

yes you're probably right but it was something that caught my eye in one of the theory workbooks which I found interesting and wanted to know more about...I'll think twice before I post another question now in case I have another scathing reply!

I wasn't intending to be scathing. It's just that music theory ins a massive and complex subject - and often the answer to a question comes back to the way in which the conventions of notation are applied. If you become more familiar with the basics you'll have as many questions, as there are always more questions. Which is what makes it so fascinating.

It always helps to have a rather thick skin on online forums - this one is very gentle one compared with one that I frequent, and on which several brainy and academic types post, erm, 'direct' responses to anything that is perceived by them as a 'stupid' question. I actually don't mind that - it keeps one on ones toes - but it can be quite a hostile environment for more gentle types.

When I was learning about farming - starting from a very low starting level of knowledge - a very wise farmer told me to ask away about anything ... and however 'stupid' the question, he always came back with an enlightening response. I learnt quickly.

In fairness to Alicia, pseudonym, I think the wording of your OP on this thread was perhaps unfortunate (and asks a different question to that which you intended), and it's very easy to make mistakes and misunderstand people in online environents.

In the orignal post, it sounds (based on the way you have worded the question) like you think that C#, C natural and C flat are all the same note which does (rightly or wrongly) suggest that it might be useful for you to cover some more basic theory first. It may not have been what you intended to ask, but your question "would you write the C# as a C natural or C flat" does make it sound like you think these notes are the same and are fully interchangable - which is a very basic misunderstanding of theoretical principles. Yes, you may well in reality understand the difference between C#, C natural and C flat - but if you look back at your OP with fresh eyes you'll probably be able to see why it sounded like there was a gap in your basic understanding which would need to be filled in before looking at more complex ideas.

I suspect that the question you have asked in the OP is rather different to the question which you intended to ask. Yes, you know what you intended to say (even if it isn't what you wrote) - but you can't guarantee that other people will know that you'd intended to ask a different question to what's actually written. It's probably worth spending a little bit more time thinking through the wording of such questions, and thinking about how they might sound to people who don't already know the question which you are trying to ask, in order to reduce the chances of people misunderstanding your question. I'm not saying don't ask questions (and nor is anybody else) but it is worth thinking about different ways in which a question could be understood by readers - especially if it's something which you are confused about as this can mean you're more likely to ask a question which sounds different to what you intend.

I'm not saying any of this to have a go at you, or anything like that - I'm simply trying to highlight one of the big pitfalls of online communication, i.e. how easy it is to write something which sounds very clear to you but is misunderstood by others.

Diminshed 7ths are really useful. They are one of the easiest ways to move between keys when you are trying to put together an arrangement in double quick time.

And they are not scary like augmented 7ths; diminished 7ths are rather more, er, subversive. Like, er, "how did we get here?"

The useful thing about diminished 7ths is that because they are built on 3 minor 3rds there are only 3 different dim 7ths. This means that for example a diminished 7th built on the 7th degree of the scale - lets say the 7th degree of C major which is B, D, F, Ab - is also the diminished built on the 7th degree of Eb major (D, F, Ab, B), the 7th degree of Gb major (F, Ab, Cb (ie B), D natural) and the 7th degree of A major (G#(Ab), B, D, F natural). There are more things that it could be but the point is that aurally they all sound the same but are just in different inversions. This in short means that it acts as a kind of pivot chord allowing you to modulate to a huge number of keys (I always imagine it like the little turny roundabouts you get in toy train sets where you drive on from one direction, spin the thing round to the direction you want to go and drive off). There is a wonderful one at the end of part 1 of the creation.

In terms of hardcore foruming, has anyone ever been on the amazon forums? pretty unfriendly.

Oh and I think briantrumpet probably meant augmented 6ths as opposed to augmented 7ths. I mention it not to be nit-picky but because it got me thinking about whether there could be a chord which was aurally perceived to have an augmented 7th in it - interesting!

Theoretically, an augmented seventh would be one semitone greater than a major seventh, so from C it would be B#

Of course, you'd need to have a very specific reason why you'd be writing an interval of C-B# rather than just a straight octave in standard practice (yes, I'm aware that temperment depending, B# is not directly equivalent to C, but try finding B# on a modern piano keyboard...)

I've been trying think of the function it would have but I can't imagine that it would ever have a different function to the perfect 8ve (apart from to sound pretentious at parties!)

Not exactly a function, more an accident: you write an orchestral score which starts in a sharp key but modulates briefly into the key of Db major. You need, in a sub-dominant chord, an octave between your bassoon and your clarinet in A. The key signatures are five flats for the bassoon and four sharps for the clarinet (yes, she would be better off in three flats on her Bb instrument, but she didn't have time to change). The clarinet note is written A natural, which is, strictly speaking, an F# in concert pitch, an augmented seventh above the Gb in the bassoon part.* Of course, you can say the part is really for clarinet in Bbb, giving you a correctly notated perfect octave, but people rarely do.

* She will use her ears to tune it as an octave.

I was hoping that kenm would come to the rescue with his erudition.

Actually, I think my thinking and nomeclature has been a bit confuddled. Aug 7ths in jazz/pop notation, written, for instance as C+7 or C7+5 have an augmented triad with a minor 7th on top (e.g C E G# Bb). That's not what I was referring to.

I had thought of aug 7th chords as being three major 3rds stacked up (C E G# B#), but can see that that would have no practical harmonic use (pace kenm's example). Anyway, from now on I shall try to remember to call them augmented triads when that's what I mean. They're still scary, but only enough to raise the eyebrows, so don't have nightmares.

In jazz chord progressions you quite often find that a diminished 7th chord is effectively a rootless 7b9 chord and is acting as the V in a minor ii-V-i progression.

Yeah you get them in classical progressions as well, they're known as incomplete dominant minor 9ths (another good one at parties!). Purcell uses them all the time.

You'd probably come across augmented 7th chords in harp music as well. Although it wouldn't really behave differently, unlike a german aug 6th which behaves differently from a dominant 7th even though they are enharmonically the same. I hadn't thought of the C7+5 though.