Is a G+7 an acceptable sub for G7b5?

FattMusiek · #1 02-10-2010, 05:30 PM

I'm looking over this page, which talks about minor harmony:
Chord Progression #3 : Minor Harmony on Jazz Guitar

Down a ways where it says "I VI II V and friends" it tells you to play a G7b5. I am wondering if a chord like this...

http://jguitar.com/chordname?string5...g1=x&string0=3 (I hope it shows it correctly)

...is an acceptable substitute. I believe G+7 means G augmented 7th.

I can reliably make a G7b9 on the A string (10th fret) but I need some help on making it with the root on the low E. An example would be if I were doing a D-7b9 with the root on the E string, the b9 is very hard to hear and is buried.

FatJeff · #2 02-10-2010, 05:41 PM

Here's a cool thing:

A dominant 7th chord can be voiced using a fully diminished chord based on any of its chordal members (notes) other than the root. So, for example, G7b9 = G B D F Ab. So you can just do a diminished chord based on any of B, D, F, Ab.

Bdim7 = B D F Ab
Ddim7 = D F Ab Cb = D F Ab B
Fdim7 = F Ab Cb Ebb = F Ab B D
Abdim7 = Ab Cb Ebb Gbb = Ab B D F

These are all rootless voicings, but the ear hears the root anyway within the context of the chord progression. (Or, the bass player plays it.)

Another nice thing is that the actual shape of a fully diminished 7th chord on the fretboard stays the same no matter what its inversion. So you learn one shape and you have 4 chords.

BigDaddyLoveHandles · #3 02-10-2010, 05:42 PM

In that first link, I see G7b9, not G7b5. Does that change anything? Rather than worrying about substitutions, if you want G in the root on the E string, play this:

3x3434 (G7b9)

FattMusiek · #4 02-10-2010, 06:07 PM

Oops...made a silly.

musicjohnny · #5 02-10-2010, 07:35 PM

Quote:

Originally Posted by FatJeff

Here's a cool thing:

A dominant 7th chord can be voiced using a fully diminished chord based on any of its chordal members (notes) other than the root. So, for example, G7b9 = G B D F Ab. So you can just do a diminished chord based on any of B, D, F, Ab.

Bdim7 = B D F Ab
Ddim7 = D F Ab Cb = D F Ab B
Fdim7 = F Ab Cb Ebb = F Ab B D
Abdim7 = Ab Cb Ebb Gbb = Ab B D F

These are all rootless voicings, but the ear hears the root anyway within the context of the chord progression. (Or, the bass player plays it.)

Another nice thing is that the actual shape of a fully diminished 7th chord on the fretboard stays the same no matter what its inversion. So you learn one shape and you have 4 chords.

Nice tidbit of info there Jeff, thanks alot.

FattMusiek · #6 02-10-2010, 11:19 PM

I've read that there are essentially three types of fully diminished 7th chords: those that contain C, those that contain C# and those that contain D (or their enharmonic equivalents such as Ebb being equal to D).

Now my question is this: say I have a B D F Ab. This "should" resolve to C since the root is B. If you say D is the root (and respell the chord? D F A Cb), then it can resolve to Eb...is this right? I'd like to be able to think about it just like "B D F Ab can resolve to so and so key."

randalljazz · #7 02-11-2010, 01:39 AM

not 'three types' of diminished 7th chords--just three diminished 7th chords, period. common 'resolution' for a diminished 7th is as a leading tone to tonic. any chord member can be considered the root, so any dim7 can resolve to four different tonics.

be aware that diminished 7th chords do have other functions, if you encounter one that is not resolving in the leading tone manner.

FattMusiek · #8 02-11-2010, 03:35 AM

Secondary dominants, you mean?

randalljazz · #9 02-11-2010, 05:03 AM

Quote:

Originally Posted by FattMusiek

Secondary dominants, you mean?

not sure what you mean. if you mean "other functions", then no. dim7 resolving up a half step (leading tone dim 7) is functioning as a dominant, whether to the tonic or as secondary dominant. same function.

this is the most common usage, and it has several applications, not always immediately obvious. (dominant, secondary dominant, modulation-pivot chord, leading tone to a chord member other than its root).

other functions would include:

substitute for tonic (same root), as in measures 3-4 and 35-36 of cy coleman's witchcraft, to lend variety. in this instance, it sounds rather like an upper leading to the ensuing ii7 chord.

substitute for tonic half step lower, as in the bridge to cole porter's it's all right with me.

non-dominant passing chord with chromatic root movement, as in measures 3-4 and 19-20 of jobim's corcovado.

non-dominant passing chord ("upper leading tone"), as measure 2 of wave.

others infrequently encountered which defy ready analysis...

Reg · #10 02-18-2010, 09:22 AM

Hey Randall.. how goes...I think FatMusiek was talking about actual notes in a Dim. 7th chord, not sure he was implying any function or voice leading practice. Jazz doesn't always follow traditional harmonic practice and voice leading as you mentioned. Which is cool... You covered the trad. functions, the chords ascending, descending or auxiliary, same root. What are your sources for Dim.7 chords, harmonically, 7th degree Har. min etc.. I saw you mentioned use as modulation pivot chord. Was that like duel function, or pivot by way of one of the four possible reharmonizations of Dim.7 chords two tri-tones, the four V7b9s. Anyway I dig your understandings and am just searching for more ways of looking at music. Thanks Reg