I see that 3 minor 6th intervals can fit into the diatonic scale, but I never see any mention of flat 6th chords in any chord encyclopedia or diagrams etc...

So whats with these chords not making an appearance anywhere? I suppose one explanation could be that inverted seventh chords cover them so there's no need for any mention of flat sixth chords, but then using that logic would contradict how I always see major sixth chords written in every chord book/encyclopedia?

  • Same with #6ths?
    – Tim
    Commented Aug 23, 2015 at 7:50
  • 1
    @Tim #6 voices are more commonly known as b7 tensions.
    – Kirk A
    Commented Aug 23, 2015 at 11:20
  • 2
    I concur with the poster's original question, and keep minb6 chords in my library with the following comment: "Many people will assert that this chord does not exist, and that these voices should be identified as a maj7 chord (using the ♭6 as root). While that may be true in isolation, I prefer to identify as it relates to its context in the Phrygian and Aeolian modes."
    – Kirk A
    Commented Aug 23, 2015 at 11:22
  • @KirkA - yes, I'm well aware of b7, as used in dom. 7ths, but it would never need to be called a #6 in those situations. And I can't think why a #6 would ever need to be called such.
    – Tim
    Commented Aug 23, 2015 at 19:26
  • @Tim #6 is the key element of an augmented 6th chord (French, Italian, or German). Commented Aug 23, 2015 at 21:15

5 Answers 5


If you see it from a pure classical standpoint, a 6th can never be a part of a chord-signature. Every chord is built by adding another 3rd to its predecessor note - starting from the root note. So you only get 1 3 5 7 9 11 13... Even a chord like e.g. C6 is interpreted as a minor 7th chord with the 3rd of the chord as root -> A C E G (1 3 5 7) -> C E G A (3 5 7 1).

In modern chord theories you'll find these naming conventions that allow a e.g. Cm6 to be seen as 1 b3 5 6. But also here you get a limitation - being that only if there is no 7th included this 6th may actually be written out as 6th. So there can be a C 6/9 or a Cm6/9 but if a 7th is included it has to be written as 7/13 or simply 13. Every tension bigger than 7 (this being 9 11 13) does automatically include the 7th, so there's no need for writing it explicitly into the signature.

You also see that this explicitly written 6th in a 6/9 chord contradicts the rule that every tension bigger than 7 includes automatically the 7th. There is NO 7th in a 6/9 chord. And of course in all these examples I am talking about the flat seventh 'b7'. Otherwise there had to be an indicator maj7 to tell that we are not talking about the flat one...

So this 6/9 chords do always have TONICA functionality (root) and not DOMINANT functionality!

Of course you will find chords like e.g. C4/7 which may also seem to be a contradiction to the above said. But this 4th isn't actually a tension like 7 9 11 13 it is rather a Csus4/7 chord which means at some place it will get resolved to the 3rd -> sus4-3. The same thing happens to a sus2 chord which will very likely become a sus2-3 later on. So you do not want to write these chords as 9th respectively 11th chords because they do not include the 7th. They rather omit the 3rd by suspending it with the 2nd or 4th. Thus the notation says 'sus'.

That is why you will never find a 11th chord but rather a sharp 11th (#11). Here the tension is two half steps away from the third and doesn't interfere. Every 11th is very likely to be an incorrect notation of a meant-to-be sus4 chord. And also chords (very typical for 80's style american pop music like Barbra Streisand and the like) like C 9/#11/13 are incorrect notations, because what they typically want to achieve is C - D/C... - a very nice progression - but better written down like this! Because the notation C 9/#11/13 would automatically include the 7th which would totally break the charming character of the C - D/C progression, especially when the thirds are the highest notes in the two chords...

(G C E over the root of C -> A D F# over the root of C).

The scale over this progression is somewhat LYDIAN like you can hear it in almost any work of the grand-master Lenny Bernstein -> MA-RI-A from Westside Story or the OUVERTURE from the Musical Candide. Also Ennio Morricone uses it a lot (Harmonica in 'Once Upon A Time In The West' etc.)

The last thing to mention here is a phenomena like you will find it in e.g. John Lennon's song 'Imagine'. Here the right hand of the piano changes between a 'D E G' (2 3 5) chord over a root of C and a 'C E G' (1 3 5) chord. This is no sus2 chord because the 3rd is already there (E). So this is an additional note for the chord an has to be written as add2 or add9. This add prefix is simply saying that there is no 7th automatically included by tensions bigger than 7 (9 11 13) and that the 3rd is not omitted like in sus chords. And to that it resolves its intrinsic tension to the root note of the chord D-C-D-C-D-C...

So you will most likely have no root note or octave of the root close beside this add9 (because it acts almost like a sus chord - but going from 9-8 -> add9-8. (So you could definitely call it a sus9 chord -> sus9-8 ;-)

But I personally like it better and find it more correct when it is written out as add9 instead of add2 because that indicates much better the stretched rubber band effect that the 9th causes - and wants itself to get relieved by lowering this tension to the root (8th / 1st).

So as to your question - a flat 6th will most likely be a flat 13th (b13) in a 9/b13 or a 7/b13 (b13) chord and have DOMINANT functionality!

As a sharp 5th (#5) it can have both - TONICA (root) and DOMINANT functionality. But this #5th has to be raised one half-step further in the following chord [D# - E] . This leads to a 6th if the root stays the same (some kind of TONICA functionality)

G #5 -> G6
(G B D# -> G B E both over a root of G)

or (when the 7th is included) to the 3rd of the TONICA (root) chord

G 7/#5 -> C
(G B D# F over the root of G -> G C E over a root of C)

In this case the G 7/#5 has a DOMINANT functionality!

And - of course - when it gets jazzy a DOMINANT chord like

G 9/#5
(A B D# F over a root of G)

can advance to

(G B D E over a root of C)

Here the tension of the 7th (F) becomes the 3rd (E) of the root chord, the #5th (D#) DESCENDS to the 9th (D) of the root chord and the 3rd (B) stays on its place to form the maj7 of the root chord Cmaj9...

Hope that helps!


Well there is a chord that fits that description if you look at it that way, but you would never call it that.

The actual chord is an augmented major 7th chord which built on C would be a C+M7. With a root of C it is spelled C, E, G#, B which can be respelled E, G#, B, C.

The reason why you'll never see it called an E b6 is one it look way too much like Eb6 (an Eb major with a 6th) and that even if the chord is in an inversion because it's functioning as an augmented chord and you wouldn't perceive the E as root.

  • But it wouldn't be an E major b6, it would always be an Ebminb6.
    – Kirk A
    Commented Aug 23, 2015 at 11:15
  • @KirkA it has the exact same issue as the other i mentioned. You'll hear it much more as a major 7th chord than any type of 6th chord be use of the dissonant minor 2nd.
    – Dom
    Commented Aug 23, 2015 at 19:31
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    As this is the accepted answer, I'll comment here. One, while in the Jazz world #5 is often referred to as b13, it seems that this chord would be a bit different than what the OP is suggesting; I would be expecting that the chord would have a perfect 5 to meet the thought process of how such a chord is not encountered. Two, there are 13th chords used in Classical music that contain a b13. I would suggest that the reason we don't see these chords in nearly any setting with any sort of frequency is that they are very dissonant by nature and b6 would have a strong desire to resolve to 5. Commented Aug 24, 2015 at 12:34

One answer about b6 chords is that they are ALMOST ALWAYS mis-identified as such. In almost every real book/fake book/chart, if you see a b6 chord it has an enharmonic equivalent spelling that makes far more sense in the harmony analysis than the b6 chord spelling does.


I think that, in harmony, a flat 6th should never be used to describe an augmented 5th, which tends to resolve upwards chromatically, as in G7+ (G B D# F) resolving to C major. I also believe that a diatonic 6th over a major or minor triad is actually a diminished 7th, and that the resulting chord can often function as a dominant. This explains why a 6th in the melody works so well over a chord that contains the scale's flat 7th, when they are a half-step apart. Happens in blues-influenced music. Comments eagerly awaited - I know this is "right" by the way it sounds, but I'm a vernacular musician, so I want to hear the formally trained person's take on this.


You know that The Cb6 (C Major Flat 6th) Chord Sounds like an AbaugM7 chord to a lot of people, I think that b6 chords cannot be used to describe a #5

Cb6 contains C, E, G, Ab

You will have Cm7/b6 for a minor 7th better sounding, you will have "mb6b9" for phrygian and "b6b9" for phrygian major.

They are very common in film scores.


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