7b9 chords

[yueni]

What are these chords all about. Could someone please explain the theory behind this chord and why it is used? Cheers.

[skei]

I'm no pro, as I'm sure you know if you've been following these fora. But the theory , well, you lower your 9, and you obviously have your minor 7, and I use it in a turnaround and as a sub for my D7 in a 251 in G, where I take a Bm7, a Bb7b9, a Am7, and a D7b9 and round it off with a Gmaj7.
It sounds very smooth and, while I don't know too much theory, well, it sounds good...
(but then again I'm no pro, so never mind)
Peace
&
turnarounds
Skei (the try everything, know nothing one)
I'm sure someone will correct me, since I only listen, I don't know the theory behind it...

[mr. beaumont]

there's a lot of tension in the 7b9 chord...you'll see them commonly as the V in a ii V I. really, the "theory" or reasons to use a chord is all about melody, voice leading, and context.

they can be used to create nice voice leading, like in this example, a ii V I in G

Am7: 5x555x
D7b9: x5454x
Gmaj7: 3x443x

see how the top note moves down a half step in each chord?

[Sailor]

Like Mr. Beaumonts definitive example. Also First four chords of Stormy Weather;

FM7 - D7b9 -Gm7 - C7b9 - (FM7). Creates a secondary dominant, vi (Dm) changed to V7b9 of ii , also V7 of F, C Dom7, altered to include b9.

Sailor

[bojan]

yueni,
in my limited knowledge (and unlimited ignorance) the 7b9 chord functions as a dominant (V7) implying in its upper structure the sound of symmetrical diminished chord, while it also can be used to support non-diatonic bass in a passing chord (say, to a iim9) or as a brief (one bar or less) modulation.

[AZanshin]

Has anyone got any comfortable voicings of the 7b9 chord on a 6th string root

[shoome]

if you want to fully play out the chord, the easiest way seems to be playing a dim chord a 7th over your root:



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A more comping-friendly (imo) would be this version, but this would leave out the 7th in your 7b9-Chord. (though in most cases this should be no problem, since the bass will most likely play out the 7th...)



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(examples are for D7b9)


I'd also like to add (regarding to the question, where and why it is used), that in a minor ii-V-i the V actually already is a V7b9, since it's traditionally based on the harmonic minor scale.

[JohnRoss]

Originally Posted by yueni

What are these chords all about. Could someone please explain the theory behind this chord and why it is used? Cheers.

From the top. You build a 7b9 by taking a dominant 7 (G7 - G B D and F) and adding the flattened ninth (for G7, Ab). It has the same notes as a diminished chord built on any of the chord tones including the b9 but except the root. So G7b9 (without the root) is the same as G#º, Bº, Dº or Fº. This multiple quality makes it very useful for taking the harmony where you want it to go.

More basically, the 7b9 is a possible V and a possible vii in minor keys.

Its most straightforward use is in a V-i (e.g., G7b9-Cm). The b9 is the minor 6th from the tonic, so it corresponds to a descending melodic minor scale (not jazz melodic minor, that's another thing), or even a harmonic minor. You hear this in tunes like St James' Infirmary.

In a minor key, vii is really a diminished chord (G#º in Am), and it pulls towards IV (the relative major), so if you add the G natural to the viiº and put it in the bass (as I did in the first paragraph, but backwards), it turns the diminished into a 7b9 and reinforces the major "feel" of the IV (e.g., in Am, G7b9-Cmajor). Can't think of an exanple offhand, anyone?

In major keys, the 7b9 is often used for VI-ii (A7-Dm). Here, the unflattened ninth would be truer to the key, and including the b9 is actually a kind of temporary modulation (to Dm or F), so it feels like the harmony is moving more dynamically. It's a trick that was heavily overused by Tin Pan Alley hacks and can sound very clichéd, though. You hear it in tunes like All of Me.

If you want to use a 7b9 as a V in major keys, as Mr Beaumont suggests, you're going outside the key a bit (that's just me grumbling because I don't really know the theory behind it). In combination with b5's, you can make the sort of chromatic melody line you get in that romantic swing stuff - if you're chord-melodying Nuages, for example, in F, you need to begin something like this:
Lead in bar on F, then
Db9 / / Db7b9 Gm7b5 / C7b9 C7 / Fmaj7 / F6 / etc.

(I believe you have to dig into Debussy and such to get the theory behind this sort of thing, but I honestly don't know.)