Why is this a G7b9?

Question

My understanding is that one approach to naming a chord is to first identify the root. However in this case, if this is really a G7b9, the root 'G' does not appear in the chord. How am I supposed to tell that this is really a G7b9?

I do know that the function of the chord matters i.e. this is really just a V-I cadence. So I guess in that sense, I understand why one might call this a G7b9. But by looking at the chord in isolation (without the context of the following C major chord), can we tell that this is a G7b9?

Answer 1

What jazz pianists mainly do is not write chord symbols for given notes. It's the other way around: what they do is, look at already written chord symbols (or even better, know the changes without staring at a music sheet) and make an artistic contribution by coming up with notes. Or a jazz pianist may even improvise everything about the chords and their realization, but now you're reading a book that has chord symbols and staff notation. If the book is about jazz piano, written for aspiring instrumentalist, then I think the examples in the book should be looked at like this:

The chord symbols do not try to be a theoretical description of the notes. And the notes don't try to be a theoretical explanation of what the chord symbols mean. The notes are an example of one possible practical realization of the chord symbols. And not just practical, but even an artistic, tasteful realization that the player subjectively likes.

What comes to this particular book, The Jazz Piano Book by Mark Levine, the author has in a way formalized the jazz practice of approximating "official" changes and improvising the final details on the fly. Whatever kind of major chord it is, if it's not a dominant chord, Levine uses ∆ as a generic symbol. Quote from the introduction of the book: (which I recommend reading, if you're using the book)

The unhappy fact that the chord symbols C, C∆, Cmaj7, CM7, C6, and C69 all mean pretty much the same thing and are often used interchangeably can be discouraging to a beginner. In this book, I’ll use the ∆ symbol for all major chords.

(Note how that confusing and unusual notation was intended to be good for beginners!?)

And since this is now the accepted answer, I'll adress your question just to make it clear.

How am I supposed to tell that this is really a G7b9

Like explained above, "G7b9" meant something that was assumed to be given in the lead sheet. Or actually, even an approximation of what there might be in an actual lead sheet, since Levine combines many chord types under a generic symbol like ∆. So, whatever notes are written on the stave, that's Levine's artistic choice of what you could play - and he chose to use a rootless voicing in his example.

To understand Levine's enharmonic spellings, you need to know how he selects scales to use, and the spellings may not be based on the key signature of the current key. It's explained in the book, but an example is in the question Db in realization of "A7alt" in Levine's piano book

But that's not all. The spelling of b9 of G7b9 as G# does not follow Levine's own logic. Look at Figure 9-28 on page 76. If you should equate the G7b9 chord with a G half-whole diminished scale, then there is no G# in that scale - if written according to how Levine presents it in chapter 9. But the G# is not a bad thing, because it lets you clearly see the E major triad there. Which might be why Levine made the mistake of not following his own scale system. Maybe he simply looked at the notes as an E major triad and wrote down what he saw.

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EDIT. The following is my original thoughts about the G# spelling, before reading the book:

What comes to the enharmonic spelling of the G# note, if it's "b9", shouldn't it be an Ab? I see that E major triad as something that a jazz player would actually think about, a pianist, guitarist or a sax player just the same. When you see the chord symbol - a dominant chord - you might think "I'll play a major triad rooted a minor third below the dominant's root". So: you see "G7", you play an E major triad over it. If you want to advice the reader to look at it as an E major triad, then the spelling E - G# - B is exactly right and proper and correct.

If you think about a half-whole diminished scale over a dominant chord, which is a common style in jazz, then you can take any chord that's found in the scale and move it up and down in steps of three semitones, and you'll stay within the diminished scale. For example, take a G major, you can move that in steps of three semitones: G major, E major, C# major, Bb major. Worrying about "correct" enharmonic spellings for these is completely missing the point of what you should be thinking about here. In any case, as a jazz soloist, you're trying to make the listener feel ambiguous about the harmony and come up with things that could enharmonically exist in many different keys although maybe with different names ... the final "correct" spelling, with the advantage of hindsight of knowing where the harmony actually eventually went, might be different from how it's good to think about it while playing.

Answer 2

With a Tritone for the left hand and a major triad for the right… an experienced jazz pianist would immediately recognize this as a rootless upper structure voicing.

So without any context, the options are either Db7#9 or G13b9.

The next chord (a rootless fourth voicing) helps to narrow it down to G13b9.

Answer 3

But by looking at the chord in isolation (without the context of the following C major chord), can we tell that this is a G7b9?

We can't. Without context I could call it E7b9 (although 9 in bass is rather unusual). So is it then not G7b9?

This seems to be a demonstration (or transcription, it's from Levine's book, isn't it?) of how an instrument (piano in this case) can realize particular harmony. The author chose to play tensions: 3 (doubled!), 7, b9 (spelled G# instead of Ab) and 13.

Tensions typically carry most of the information about harmonic motion. Fifth and root are more "boring", and in jazz are often omitted by the chord instruments. Moreover, in a band there are other instruments, in particular bass and melody instrument, which may play the tones that you omit. This even has a name: rootless voicing.

In classical music root of a 7b9 chord is also sometimes omitted, and results in a diminished seventh chord.

Answer 4

In addition to other good points made:

For me, in the context of jazz standards like "What's New?", with the piano left hand in that range, that tritone F B is the dominant feature, with whatever-it-is in the right hand being "just harmonics". Even without seeing the C-chord next (yes, as other have said, a C6/9...), I would wager that that first measure is either some kind of G7, or else Dflat7, because of that tritone.

Either way (depending on the ambient key signature), I very often see this kind of "mis-spelling", and it's usually for some sort of readability... especially if one is thinking about "stacking" things. So although my reaction is that it's not really an Emajor triad in the right hand, I certainly have no problem knowing how to play it immediately. :)

Again, in this range, the tritone in the left hand is decisive for me. The details about higher harmonics might matter for voice-leading, etc., but the function is V7 (in some key).

Answer 5

Probably because it came from a jazz resource where authors notoriously combine chord names or Roman numeral analysis with enharmonic misspellings.

Second you may not know about rootless chord voicings in jazz. Typically, rootless chord voicings involve the chord root played by some bass instrument, like the piano left hand or an upright bass player, and then the 'rootless' chord is a voicing of the other chord tones and extensions in some higher range instrument like the piano right hand or maybe a guitar.

So, for example, the bass could play a G while the piano in mid-range plays F B E to combine into a G7. Note that many lead sheets or jazz analysis might just write such a chord as G7 and not literally G13 to account for the E. That last point has been discussed in other posts about chord symbols and chord extensions.

F B E G# B enharmonically respelled as F B E Ab B as numeric chord intervals gives us 7 3 13 b9 3 where we can more easily see the flat ninth. The original spelling with a G# above a root of G technically gives us a #8, an augmented octave obscuring the flat ninth.

...the root 'G' does not appear in the chord...

Remember, in an actual performance the root will be played by someone. If this were a listening question, the perception of the root would probably be different. But, working from just the notation, the question still remains: how does one get that chord symbols G7b9 just from the given notes?

If you take either spelling and order the tones in thirds...

E G# B (D) F or B (D) F Ab (C) E

...things don't get much clearer.

How am I supposed to tell that this is really a G7b9?

You can't, and that is the nature of rootless voicings, because they are incomplete.

Let's use a different example, one more basic.

F A B E is a basic rootless voicing above G for a G7 chord.

F A B E is a basic rootless voicing above Db for a Db7alt chord, tritone substitution.

F A B E is a basic rootless voicing above D for a Dmin6 chord.

Same rootless voicing, but three different chord depending on... the root given in the bass.

You could make a similar point about incomplete voicings using the tritone. If given only the tritone of F B you could superficially say it's a G7 that would resolve to C, but in fact there is no way to tell that isn't a partial voicing of Db7, the tritone substitution that would resolve to C.

The root must be given to really know.