# When is a note b5 and when #11?

(on an Jazzology exercise) I have to identify this chord:

What I thought it was was: `G7 b5 b9 b13`.

But when I looked at the solution, it was `G7 b9 #11 b13`.

I said that the chord had `b5` because of the Db; since D is the 5th of the G chord, I supposed that Db would be b5.

Can a b5 be considered as #11? Like, in this example I would have to consider that Db is C#, which actually is #11.

Could it be that the Db is on the higher staff than the root note? If it was on the low staff, would it have been considered as b5?

• IMO, if they write it as d♭ then it must be a d♭ and not c♯, so it can't possibly ♯11. But then again, Jazz guys tend to treat enharmonics in a way I often don't agree with, so... – leftaroundabout Aug 4 '14 at 19:44

I would say that your answer is actually correct and the book is wrong in this case, and let me tell you why. It seems likely that this is a very modern book and that if they would say it is a #11, they wouldn't penalize you for writing the technical correct b5.

Chords are based on scales. In a typical 7 note scale scale, you will write the intervals as so:

1 2 3 4 5 6 7

By this, I mean that every interval is accounted for: the first, the second, and so on. Remember that the 2 is also the 9, the 4 is also the 11, and the 6 is also the 13. But I'm keeping them as 2, 4, and 6 for my example.

Take this example of a myxolydian scale:

1 2 3 4 5 6 b7

You write it like this because every note in the scale is accounted for. This is technically the same:

1 2 3 4 5 6 #6

This is incorrect because technically we are missing the seventh scale degree.

So let's think of your chord as an example. A typical G Myxolydian scale is: G A B C D E F G which always corresponds to 1 2 3 4 5 6 (b)7. The notes you have in the chord are G F B Db Eb and Ab (In scalar order, G Ab B Db Eb F) The G corresponds to the 1st degree, the Ab to the b2 (or b9), the B to the 3, the Db to the b5, the Eb to the b6 (or b13) and the F to the b7.

No matter if the D is Db, D, D#, D##, Dbb, it will always be the 5th degree in the scale: so augmented, diminished, etc. If they had written C#, it WOULD have been a #11, but since we a) are using a D when referring to a G-rooted chord and b) do NOT also have a natural (perfect) 5 in the chord, we can conclude that it is actually a b5 and not a #11.

The fact that your book wrote G7 (b9, #11, b13) even though we don't have a natural 5, is confusing. Musicians would treat this as if there would be a D natural and a Db (C#). They should include that the chord omits the D (omit 5) or write the chord as you did.

If it's a #11 then it must be written as such. As a b12 it doesn't make sense, so the dots cannot be accurate.Otherwise we have anarchy. (Again).If you can make anything of this exercise, then maybe you're past this level!!

I disagree with the previous posters in that I think there are several good arguments with opposite conclusions.

One way to look at it is that the name of a note should depend on how it is written. In this example, a Db is b5 (or b12) and a C# is #11, period. This is the standard practice in the world of classical theory.

Another way to look at it (which @Deannakov touches upon) is that in the context of a passage, it may make more sense to consider what scale is implied. In this example, if this chord appears before a C major chord in the context of a V-I cadence, the implied scale is likely G major (or G mixolydian; either way a D-natural is strongly implied). Therefore the Db is really an ornamental scale degree 4 (C#) and should be considered #11. However, if this chord appears in a more chromatic environment, say between two Ab-minor chords, its harmonic function would be a "neighbor" viiø7/I chord, and would always be spelled as a triad, thus b5. (Here, I would probably also spell the B as Cb, indicating a suspended fourth.)

A third way to look at it is that it is simply easier to sight-read the notes in the upper staff when they are all flat, as opposed to having mixed accidentals. In such case, there is little hope of settling the question by deduction, and one should just revert to whatever overarching school of thought is most appropriate: in most jazz contexts, b5 is slightly more "standard" than #11.

Given your book's solution, I suggest that the authors have invoked my situation #2 above, i.e. they consider the G dominant seventh chord to be sufficiently striking so as to imply a D-natural (therefore what is added is #11), and not dissonant enough to imply #1 (therefore b9) or #12 (therefore b13).

• If those are the cases, then it should be written as you say, #11, not b12, which, at a push, could be construed as b5, to be included in the chord with a perfect 5. – Tim Aug 7 '14 at 7:30

Jazz. Altered dominants.

You could also call b13 a #5.

avoiding the altered fifth nomenclature may indicate the 5th is included

E.g. #11 might indicate inclusion of the fifth. While b5 mans no unaltered fifth. Same goes for b13 vs #5

b9 and #9 are also used on some altered dominants - These indicate not to use the unaltered 9th

Regardless of opposing viewpoints, this naming convention is standard practice.

The book answer is incorrect. By convention, a B7(b9 #11 b13) has an unaltered fifth and also an augmented 4th (11th).

The technically correct answer for the written chord is B7(b5 b9 b13), because the written chord does not have both the #11 and b5.

The general rule is that notated available altered tensions do not replace or alter chord tones.

Ignoring all discussion and answering only the title question:

a b5 means you are replacing the 5 and keeping all other notes (including the 4 intact.)

A #11 means you are replacing the 4th and keeping all other notes (including the 5) intact.

So the answer is: whichever is correct when used in the context of the surrounding chords and melody of the song. Does the unaltered 4 fit or does the unaltered 5 fit into the surrounding context?