With extended chords... Cm13 implies that the 7th is present and that the 9th and 11th can also be played.

Now if we write Cmb13 does this also mean that the 7th is present and that the 9th and 11th can also be added OR does it mean that the b13 is an addition and thus the 7th, 9th and 11th are NEVER played? Must the chord be written as Cm11b13 for 7th to be present and the 9th to be optionally implied?

EDIT: I'm leaning towards accepting arcioko's answer as it is the only yes or no answer to what I believe is a simple question.

EDIT2: I'll reword the question to make it simpler. Cm9 always implies that the 7th must be played. Is that also true for Cmb9?

EDIT3: Dekkadeci's comment on arcioko's answer is the answer I was looking for. I can't accept a comment as the answer though.

EDIT4: I have flagged this question as a duplicate of Does an altered 9th/11th/13th imply the full tertian stack? thanks to Dekkadeci's comment. Thank-you all.

  • 2
    Copied from comments below, seems very relevant to understand the OP question "I'm writing a chord identifier based on notes and need to know if it is possible or not." Jun 25, 2021 at 2:35
  • see edit2 for the question simplified. And yes I'm writing a chord identifier. There are problems and/or omissions in every single chord identifier I've looked at. I aim to fix every single one of those issues. Jun 25, 2021 at 7:00

4 Answers 4


You will find many different opinions, some of which are similar and some which conflict on this subject. The bottom line is there is no perfect universal list of rules when it comes to writing chord symbols. Yes there are guidelines but since chord symbols don’t specify exactly what notes to play in what order there will be interpretations and liberties taken. For example, many musicians will sometimes add 9’s or 13’s to chords that don’t have them in the symbol or add a b9 or a b13 to a dominant chord resolving to a minor chord. If you give 10 pianists or guitarists a C7 you will likely get at least 7 or 8 different results, and more than a couple will have added or omitted notes.

Regarding your specific example, the thing about Cmb13 is that it is ambiguous. Altered intervals (b9, #9, #11, b13) should carry the 7th or maj7th in chord symbols (should you desire a 7th) for clarity (Cm7b13) if you don’t want the 7th you should use “Cm(add b13)”. The other thing is it is an unusual chord symbol so most people seeing it will at least do a brief double take. They will ask themselves the same question you asked here but in a split second and then react one way or the other. It is more common to have a raised 5 than both a 5 and a b13 in a minor chord (Cm#5 or Ab/C).

Familiarize yourself with whatever fairly standard chord naming conventions there are and then:

  1. Be as clear and specific as possible
  2. Don’t make assumptions about how your chord symbols will be interpreted
  3. Expect that people will take certain liberties with your chord symbols at times
  4. If you want specific notes and voicings, write them out.
  • Ok, so my question is can altered chords such as Cmb9 imply that the 7th is played. Cm13 always implies the 7th must be played. There is nothing ambiguous about a Cm13 other than the 9th and 11th which are subjective. Your answer is ambiguous. It seemed like such a simple question. Jun 25, 2021 at 1:04
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    My answer is ambiguous? Really? Natural tensions, 9,11,13 imply a m7, I don’t argue that. Altered tensions, b9, #9, #11, b13 are rarely if ever written with some type of 7 preceding them in my experience. As a matter of fact I have never encountered a Cmb9 or a Cmb13 in years of doing gigs and reading charts. I gave you an answer that is not ambiguous but rather explains a way to make sure what you write gets played properly. Also I answered your question based on the original and not the edited version. Jun 25, 2021 at 1:45
  • Yep, it was. My original question was clear and you didn't answer it so I made the question as simple as possible. You just clarified your answer. Thanks for your input. Jun 25, 2021 at 2:48
  • P.S. 9,11,13 don't always imply a m7... could be maj7 or a dim7 too... depends on the quality. Again, thanks for your input. Jun 25, 2021 at 2:58
  • No problem, 9 11 and 13 contain a m7 unless you specifically indicate maj7 or otherwise. That’s what I meant. Jun 25, 2021 at 4:17

Cmb13 only implies the b13 note, you are right in that the chord must be written as Cm11b13, this is why chords like C7#9 or C13b9 are notated the way they are, this is because if it was like that there would be no why of knowing if the chord was C Eb G Bb D F Ab or just C Eb G Ab.

Note: A better way of notating it would be Cmaddb6, or Cm(b6)

Edit: Also, nother thing that happens is that you dont know the quality of the seventh, sure you could say that its minor based on the third but it could also be major

  • I find it extremely odd that extensions imply other notes but alterations above 7 don't seem to. Logic? Jun 24, 2021 at 12:13
  • Your answer does seem to fit with my experiences analyzing classical music (where V13 in C Major indeed only implies G-B-D-E), but I bet other users will disagree about your answer and say that G13 implies G-B-F-E.
    – Dekkadeci
    Jun 24, 2021 at 12:23
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    @greatwhitepine My personal rationalization is that the altered symbols shorthand out the word "add" as well as specifying the modification.
    – user45266
    Jun 24, 2021 at 23:24
  • @user45266 Have you ever seen anyone think that a Cmb9 implies that the 7th must be played, ever? That's the only thing I need to know. I'm writing a chord identifier based on notes and need to know if it is possible or not. That's it. Jun 25, 2021 at 1:10
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    @greatwhitepine - Answers in music.stackexchange.com/questions/114974/…, including music.stackexchange.com/a/114977/37354 and music.stackexchange.com/a/114991/37354, outright state that chords like G9 and C#11 imply that the 7th must be played. The topmost of the two indicates that Cmb9 should be interpreted like the others and have an implied 7th, while the bottommost pretty much outright states this.
    – Dekkadeci
    Jun 25, 2021 at 12:05

I'm writing a chord identifier based on notes and need to know if it is possible or not.

I think this is the question really to be answered here...

I assume we're speaking about jazz/popular music chord names (as Dekkadeci pointed out, other naming conventions exist).

  1. Chord symbols are not really meant to indicate the exact notes to be played by the musician. They leave room for interpretation: dropping or adding notes and choosing the actual voicing. A skilled musician may reharmonize the song on the fly. On the contrary, I guess you want the chord finder to output symbols as accurate and unambiguous as possible. It should be noted that these will likely not be the same as chord symbols typically used in practice.

  2. It is very common for musicians to omit notes in chords. Even a simple Cm can be played as two notes, C and Eb. Especially in very small ensembles with one–two musicians, harmony movement might be barely hinted. C7 might easily become E-Bb. Chords might be played melodically rather than harmonically. Guessing the underlying harmony might be an impossible task for a program that only interprets the vertical structures.

  3. Omitting notes is even more common in larger bands. A guitar may play Eb-G-Bb, which one would call Eb, but if bass plays C, it adds up to Cm7.

  4. Chord naming convention (and music notation in general) is based on practice and historical conventions, rather than logic. It is also very much focused on western popular music. What it implies, it's not really feasible to label any given group of notes with a compact chord symbol. Chord symbols are meant for chords that are actually used in western popular music.

In particular, I can't recall seeing a minor chord with flat 9 in jazz standard repertoire. You'd think that it's a diatonic chord built on the third step of a major scale... but somehow it's not used. So I'm following more intuition than experience. I'd say that Cmb9 does contain flat 7. I'm not sure how would I play it as a musician. Normally fifth is the first one to go, but in this case it creates a very interesting dissonance with b9, so maybe I would drop Eb? Also, C-Eb-G-Bb-Db could be interpreted as Eb13... in such ambiguous cases the voicing may matter much for how the chord is interpreted.

Concerning Cmb13, a minor chord with 6 is typically written as Cm6. I guess you could write Cmb6, but again, this is not a typically used chord (at least not in pop/jazz repertoire)... and C-Eb-G-Ab might likely be heard as Abmaj7.

does it mean that the b13 is an addition and thus the 7th, 9th and 11th are NEVER played?

b6 is addition, but it won't stop a musician from adding 9, or b7 if they feel like it... I think Laurence summarized the naming/performance rules well.


The 'pile of 3rds' is implied - except when it isn't!

C9 and C13 are assumed to be extensions of C7 rather than extensions of C. However, the 11th is normally omitted. When the 7th is not present, we use C(add9) and C(add13). Or C6. All of this applies equally to Cm9, Cm(♭9) etc.

C11 MIGHT mean the 'pile of 3rds' up to and including the 11th, but it's more likely to label a C7(sus4), C9(sus4) or B♭/C chord. Functionally equivalent but quite different colours. So be careful if you're tempted to write C11.

There's no real system to this. Just various conventions of useage.

  • While this is useful it doesn't answer my question. Can Cmb9 imply that the 7th is present? Cm9 does. Jun 24, 2021 at 14:46

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