Fully Diminished Chords and scale relation.

[Michael Henry]

A friend of mine recently asked me a question (which was mostly a compliment, I'm not the most theoretically informed when it comes to improvising over a progression), but after trying to do my best to answer I was still a bit unsatisfied. I was hoping one of you might have the ability explain this particular thing a bit further - namely scales that fit over diminished chords, but also giving me some idea if I was on the right track or not.

Basically my suggestion to him was to take a Bo chord and use A harmonic minor in the Locrian mode. This fits really well, because it's basically a C scale over a B7 chord. However, as I played through it and tried changing the position, I realized that if you invert the Bo chord by moving it up 3 frets and then attempt to play a C harmonic minor scale, it sounds incorrect. If you continue to play the A harmonic minor scale, however, it seems to work. The same seemed true for the 2nd inversion of the chord as well.

The problem is, that seems to imply that the relative scale isn't dependent on the chord being a diminished chord, but rather on the function of the chord at it's place in the progression. I also realized, however, that I was hearing this particular chord more as an E7 b9 and resolving it to A minor.

So, my question is, is there a way to break out of the mindset that the fully dminished chord acts as a V chord, or even a V/V chord, or am I simply locked into hearing the traditional functional tonality? If a fully diminished chord is used at a non-cadential time, what scale(s) go along with it?

(I hope I'm making sense... If you play a Bo chord, then play through A harmonic minor, followed by an E7 chord and resolving to Am, you'll hear what I'm hearing - my desire is to not be so rigidly functional - something other than V I or V/V V I.)

[ksjazzguitar]

Originally Posted by Michael Henry

...The problem is, that seems to imply that the relative scale isn't dependent on the chord being a diminished chord, but rather on the function of the chord at it's place in the progression. ...

Yes, function is everything. Not all dim chords are the same. If it is resolving up a half-step, then yes you can use the 7th mode of the Harm Min (I wouldn't call it the Locrian of Harm Min.) as that would just be like treating it as a V7b9 without the root. You're "moving up a m3" doesn't work because that would be treating it as a different chord - so it has a different sound (although I do know people who do this.)

But of course, diminished chords can function differently. Sometimes they are common-tone diminished chords, usually a dim chord built off the tonic (like in "UMMG") or of the b3 (like the 2nd chord in "Witchcraft.")

Sometimes this same chord will show up as a biiidim7 working as a passing chord from iii (or I in first inversion) to ii (the 2nd chord in "How Insensitive" or the chord in m.6 of "Bye, Bye, Blackbird.")

There are other cases, but in these and most others where it is truly not acting as a leading tone chord, then you probably want the WH diminished scale. (Even when using this over the leading tone diminished chords, this is fine when resolving to a major chord, implying a V13b9.)

As a side note, in some older songs, this common-tone diminished will be implied by putting a VII major triad or a VII7 over a tonic bass. This is a very common sub if a M7 is in melody over a tonic chord. It usually resolves to a tonic chord. Essentially is is a idimMAJ7. It is a nice reharm, I use it on ballads all the time. On my web site, I have a recording of me playing "Misty" where I play this as the chord on the downbeat.

Peace,
Kevin

[Michael Henry]

Cool! I'll have to work with that. And as to calling it Locrian, I wasn't sure about that and even though there's a logic to it, it seemed odd and I couldn't find a definite way of describing it differently - thanks. (I confess to thinking quite often in the church modes, and am a big fan of modal music and Hovhaness in particular.)

I'm going to play around with the things you said, I'll post if I come up with some insight or further questions.

Not to say no one else can add their input...

Thanks Kevin!

[ksjazzguitar]

Yeah, there is nothing wrong with knowing your modes, but an unqualified "locrian" mainly refers to the 7th mode of the Major scale. People come up with different names for the scale to which you were referring (like Locrian nat 6) but I find something like "7th mode of the Harm Min" to be unambiguous. You can certainly spend sometime wandering around the modes of the other scales. I find the 5th mode of the Harm Min and the 3rd, 4th, 6th and 7th modes of the Mel Min to be very useful.

Peace,
Kevin

[Reg]

Hey Michael... great points by Kevin, when you use Bdim. going to A- ... your usually deceptively implying either E7 or G#dim, which both have Dom. Resolution or if A- is the I chord, then Dom. Cadence. Or your modal interchanging from what is normally B-7b5 or your chord could really be the II chord of Harmonic min. and instead be using a B-6b5 deceptively. So if your trying to use a symmetrical dim. pattern... it is stretching the ear, I look at Dim chords as ... well I can find what I'm looking for... just joking I dig Auxiliary dim. When you say fully dim. are you referring to one of the symmetrical dim. patterns... half / whole or whole / half.
The typical sub or re-harm. is to take the two tri-tones from dim. chord and construct four dom7b9 chords built from two tri-tone and their enharmonic spellings;
C#dim7 going to D-7
C7b9
A7b9
Eb7b9
Gb7b9
The choice of which one you use is usually based on 1) resolution (Dom) of target chord
and/or normal tensions ( for the Dom chord), and above all the melody. The related II-7b5 usually imply a re-harm. Typically Dim chords are secondary Doms of expected target chord and/or
chromatic motion resulting when chords are voice lead.
There are other technique of using Dim chords but don't follow traditional practice and fall into my si-fi collection... best Reg