Why does the dominant chord contain a flattened 7th while this tone is not even in the scale?

Let's take, for example, a C7 chord. It is a 1-3-5-b7 of a C scale (C-E-G-B♭).

But the C-major scale does not contain B♭. So why do we use a flattened 7th in a dominant chord?

It sounds dissonant. I think it would be better if it would contain a 7th without an alteration, which produces a more pleasant sound.

  • 6
    Actually, the chord C-E-G-B is (or at least should be!) more dissonant than C-E-G-Bb! At least to my ear the interval C-B is harsher than C-Bb. To hear it more clearly, invert the intervals: B-C (a minor second) is more dissonant than Bb-C (a major second).
    – nonpop
    Commented Nov 3, 2013 at 13:14
  • 1
    It's all in the ear of the beholder.Don't forget there are 3 main '7th' chords - Cmaj7-C E G B. C(dom.) 7-C E G Bb. Cm7 -C Eb G Bb. Not forgetting the ephemeral Cm maj7 - C Eb G B.It's so important to be clear as to which you speak about.
    – Tim
    Commented Nov 3, 2013 at 15:15
  • @nonpop: you could argue the ideal minor-7th should sound less dissonant because the 7th harmonic overtone is in some scales on that interval, but at least in well-tempered tuning it's actually quite a lot off. The inversion, i.e. major second does sound good because here it's the 9th harmonic that matches, indeed quite well even in well-tempered tuning, but I don't think that's significant in 7th chords. And we also need to consider the other notes: both e and g harmonise much better with b than b♭. Commented Nov 3, 2013 at 20:28
  • 2
    Because C-E-G-B is a Cmaj7 chord. All "dominant seventh" chords are major triad+minor seventh above root. All major seventh chords are major triad+major seventh above root. See this Wikipedia entry on Seventh Chords for more info. Best of luck. Commented Jul 28, 2016 at 21:28
  • 1
    Comments are not for extended discussion; this conversation has been moved to chat.
    – user28
    Commented Jul 29, 2016 at 14:53

18 Answers 18


Dominant is the fifth chord of a scale. For example in the C Major scale, the G chord is called Dominant.

The 7th of G is F natural.

So the G7 chord would be G B D F, but if you wanted to have maj7 it would be G B D F#, but the C Major scale does not include F#.

The C7 would be in the F Major scale. The key to F Major scale is Bb, and the Dominant chord would be C E G Bb. (This doesn't mean that you can't play C7 in another scale.)

Edit: Now that I re-read my answer, I think I wasn't really clear. In order to find a chord, you need to ascend 3rds from the note you start (for the most common chords).

So, in the C Major scale, the G chord, which is Dominant, will be: G (ascending a major 3rd) B (ascending a minor 3rd) D (ascending a minor 3rd) F, making it G B D F. That's the reason the Dominant chord contains a minor seventh.

  • The 7th of G is not a F natural. It's an F#.
    – PaulD
    Commented Nov 9, 2013 at 20:30
  • 2
    If you are on the C Major Scale, it's F Commented Nov 10, 2013 at 7:55
  • @Jesus = there is no 'general' 7th. There's a major 7th - G - F# and a minor 7th - G-F, whatever key you're in. There's also aug 7th - not much use as it's the octave, - and diminished 7th, which is G - Fb, sounding like G - E, but still called 7th.This works for intervals and chords.
    – Tim
    Commented Dec 26, 2013 at 14:14
  • i am sure @Shevliaskovic was referring to G Mixolydian rather than G major (ionian). G mixolydian uses the same notes as C major, and thus the reference to it.
    – mey
    Commented Feb 5, 2015 at 19:31
  • @mey Shevliaskovic certainly didn't mean "G Mixolydian" rather than "G major" because Shevliaskovic didn't say "G major." Shevliaskovic said C major. The dominant seventh chord doesn't come from degrees 1, 3. 5, and 7 of the mixolydian mode or any other scale; it comes from degrees 5, 7, 2, and 4 of the major scale. That is, the G dominant seventh chord comes from C major, because it is the seventh chord built on the dominant of C major, which is G, using the pitches that are diatonic to C major, which are G, B, D, and F
    – phoog
    Commented Mar 5 at 0:41

Another way of looking at the question is this: we have a number of seventh chords, dominant, major, minor, diminished, and so on. So why does the dominant seventh get the "default" symbol of C7 whereas we have to qualify the others as CMaj7, CMin7, etc.?

The answer is that even though a C major seventh chord would fit more "naturally" in the C major scale, the dominant chord is much more fundamental to our conception of harmony (for example, in the C major scale, G7 is a very important chord because of the tonic-dominant relationship).

Gottfried Weber was one of the earliest writers to use what we would recognize as "modern" chord symbols in harmonic analysis (as opposed to the more traditional figured bass or Roman Numerals). In his treatise Versuch einer geordneten Theorie der Tonsezkunst (1817) he talks about categorization of what he refers to as "four-fold chords" (which we know as "seventh chords") saying this (English translation by James F. Warner, 1851):

The four varieties of four-fold chords above enumerated have not, like the three sorts of three-fold chords, each its own particular name. The first, indeed, (the one that has a major third, a major fifth, and a minor seventh) is often called the dominant chord; but this appellation, as we shall see hereafter, has too much of a special relativeness to be duly clear and unequivocal. Vogler proposes the name entertaining seventh; because the seventh of this chord "agreeably entertains the ear" ... Others have again called it the essential seventh chord ... Since however, it is very desirable that this particular four-fold chord, at least, should have a distinct name of its own, inasmuch as it is the principal chord of the kind, we will accordingly denominate it the principal four-fold chord ...

(emphasis added)

Later on, when Weber lays out his notation for seventh chords, it's only natural that the dominant seventh (being the "essential" or "principal" seventh chord of greatest importance) is given the simplest designation with just a capital letter followed by a 7 (e.g. C7). In comparison, for the major seventh he uses a similar notation but with a slash through the 7.

From then on, convention has kept chord symbols mostly the same over the years, with only small changes from what Weber originally used. Weber himself even commented on this in later editions, saying:

While I here ... introduce new modes of designation, I still by no means claim to have these signs adopted by others and brought into general use; but, on the contrary, my only aim in employing them is to procure thereby a convenient and intelligible language of signs between me and my readers ... But the fact that the signs, appellations, and other modes of representation chosen by me, do accomplish this object, seems to be shown by the circumstance that, immediately after the appearance of the first volume of my theory, other writers adopted them and appropriated them to themselves.

  • 2
    And a quick shoutout to Abbé Vogler, who was the first to use a system like this. Weber's system owes a lot to what Vogler was doing in the 1770s.
    – Richard
    Commented Jul 28, 2016 at 16:06
  • 1
    @Richard Good point, Vogler's contributions are definitely not to be overlooked! Although as Weber also says in the same passage, his choice of terminology "has met with no acceptance" ... funny to think if things had turned out differently, we could all be talking about "entertaining sevenths" here instead. :)
    – hopper
    Commented Jul 28, 2016 at 17:08
  • @Richard do you know of any material from Vogler related to making conventions like the one hopper indicated above? Commented Jul 28, 2016 at 19:16
  • 1
    Unfortunately, I don't. And this doesn't answer your question, but you may find it interesting (and it's related): the Belgian theorist Fétis labeled the V7 chord the beginning of modern tonality. He actually found a specific measure in a Monteverdi madrigal! So this particular chord's role as a marker and determinant of tonality further explains why it's the "default" usage of the seventh chord, hence the shorthand of C7.
    – Richard
    Commented Jul 28, 2016 at 19:23
  • Rarely see major 7th depicted with a slashed 7. In Europe the slashed 7 is the usual way to write a 7 anyway! More often a triangle, and sometimes a 7 as well. Or just 'M7' or 'maj7'. With handwritten stuff M7 and m7 are easily mixed up though.
    – Tim
    Commented Jul 29, 2016 at 7:45

It sounds dissonant because it is ! It is, and has been, for hundreds of years,the means of moving to the subdominant chord. Containing a most unstable tritone, as in E and Bb, in your example in Cmaj.,it needs to resolve to an F chord. Don't worry that Bb is not in the key of C, as it's in F, where the music is going, albeit briefly. Your idea of using a major 7th is fine, but it doesn't push towards the subdominant in any way. Think along slightly different lines - the chord that pushes back to C is actually G dom.7th, which contains a tritone, AND an F note, which isn't in the Gmaj.scale.

You'll find the #5th does the same sort of job (as in C+ - C,E,G# to move to F); again G# is not in the key. Just because you're in the key of Cmaj., doesn't mean you can ONLY use the 'white notes'.

The answer is exactly what I wrote in my answer to 'What does dominant mean in music'.

The dominant seventh chord has an extra note to the triad of 1,3 and 5. The sequence is followed, so it's a 7. That's where confusion sets in. It's not the 7th of the scale that the dominant chord would be the key of. In other words, G7, as a dominant of C, would have F natural as the 7th part of it. Not F#, which is the 7th of the G scale.

That's because G7 - a.k.a. G dominant 7th - is a chord from the C key, not its own G key. I know that sounds adaft, as we find G7 in lots of songs that are in G. However, most times, the following chord is C (or Cm), so the G7 needs the 7th part of it to be from key C rather than its own key,G.

Musically, what's happening is the 3 is a semitone below the tonic root, and the 7 is a semitone above the tonic 3. To resolve, they both move a semitone each, the smallest change possible, and everything sounds fine again. The tritone - very unstable sounding - resolves to a nice major (or minor) 3rd interval.

To put it in a simpler form - the dominant 7th is built off the dominant note of the scale, note 5. Then the next 3 notes stack, as in the 7th, 9th and 11th of the existing scale. Thus, in C, 5=G, 7=B, 9=D and 11=F. The dominant chord of C, G7. Nothing at all to do with major 7th notes. Except that note just happens to be part of the chord!!

  • how do you know that it need to be resolved exactly to an F chord? Why not Bb chord for example? And strangely, if it's named 'dominant', it must dominate on all other chords in the selected scale, I think. So other chords must be resolved into dominant, not vice-versa.
    – PaulD
    Commented Nov 9, 2013 at 20:39
  • @Jesus - most people are of the opinion that the sound of a dominant seventh chord will resolve to the chord a 4th above it. This happens in most tunes, many times. Yes, of course, you can play any chord after any other chord, but dominant to tonic, because it sounds natural, is played so very often.The theory follows the fact, not vice versa.
    – Tim
    Commented Nov 11, 2013 at 8:32

The other answers to this are all good. However, I can see how they could be confusing to many people. So here is my attempt at explaining why the 7 in a dominant chord is lowered.

First off you need the definition of the dominant 7th chord:

 Major 7th 5
 contains  3

This means, as you already know, that building a Dominant chord off of a C, would result in C, E, G, and B♭.

Now, to understand why the 7th is flat, you need to know that the dominant 7th chord only happens naturally on the 5th of a Major scale:

enter image description here

You can easily double-check me (to make sure that I am telling the truth) by first off knowing that a dominant chord consists of a M3 (1 to 3) a m3 (3 to 5) and another m3 (5 to 7).1 Now, what is the interval between G and B? Yep, a Major 3rd (M3). And between B and D? You guessed it, a minor 3rd (m3). And finally another m3 between D and F. You can also double-check me on all the other 7th chords by checking the intervals between the four notes to see if they contain the right intervals for the given chord. I.E. Major 7th: M3, m3, M3... Yep.

So now that we have proven that a 7th chord built off of the 5th of a key is truly a naturally happening Dominant (you believed me anyways, didn't you?), we can easily see how the B in a C dominant 7th would be a ♭.

Think about it. Since the Dominant 7th chord is naturally occurring on the 5th, let's find a fifth below C. That's F, isn't it? Here are the naturally occuring 7th chords in F major:

enter image description here

Look! The fifth is a naturally occurring dominant chord containing C, E, G, and B♭! (don't forget that key signature!)

So that is why we end up with a B♭ in the C major key signature. It's because the Dominant 7th chord is really based off of the Key a P5th below.

1 http://www.socraticmethod.net/music_theory/seventhchords.htm


The "dominant seventh" is so called because it is the result of adding a 7th to a V chord of a major key (called the dominant chord) without an accidental. For example, because C is the dominant chord of F major, the notes of a C7 chord should agree with the key signature of F major. The reason the 7th is a Bb is that that note is part of the F major scale.

I personally favor using the term "dominant seventh" only in cases where it is either the dominant chord of either the key signature or is dominant relative to the following chord, a concept called "secondary dominance". For example, if the song "All through the night" is played in C major, the opening chords are:

   C      F            D7         G
   Peace, my child let God attend thee

The D7 chord is the dominant chord of G, which would be the dominant chord of C major. Because the D7 chord is going to resolve into G, it uses the nodes of the G major scale, which includes an F# but not a C#. That particular chord I would refer to as a "dominant 7th" because it is the dominant chord of the following chord to which it resolves. There are some other contexts, however, in which that same shape of chord is used but does not resolve in that fashion. In such cases, I prefer to refer to that chord shape as a "major minor seventh", meaning a major chord with a minor seventh [relative to the root] on the top.

  • 1
    That D7 is known as a secondary dominant. There is absolutely no need to put (#3). It makes no sense - I thought you meant play F## in the D7 chord, which obviously it doesn't. When a chord has just a 7 after it, as it is the most used sort of 7th, it always means dominant, so will always have a major 3rd. The main place to find unresolved dom.7ths is in Blues.
    – Tim
    Commented Nov 4, 2013 at 7:44
  • 2
    From the standpoint of someone playing chords, you are correct that the chord names are interpreted without regard for the key signature. My intention was to make clear that secondary dominant sevenths have accidentals because their pitches are what they would be in the key of the chord they lead into. I'll tweak the way I wrote things to make it clearer.
    – supercat
    Commented Nov 4, 2013 at 17:06
  • @Tim: In any case, my point was to mention that a major minor seventh is often called a "dominant seventh" because the dominant chord is the only major chord whose seventh will naturally be a whole step below the octave.
    – supercat
    Commented Nov 4, 2013 at 17:14
  • Never heard it called a 'major minor seventh'. There is however a 'minor major seventh' chord.
    – Tim
    Commented Jul 19, 2017 at 22:26
  • 1
    @Tim: A minor major seventh is a minor triad with a major seventh added; a major minor seventh is a major triad with a minor seventh. Because that is the most common form of seventh chord, the term "seventh chord" refers to that kind unless specified otherwise.
    – supercat
    Commented Jul 19, 2017 at 23:06

Why does the dominant chord contain a flattened 7th while this tone is not in the scale?
Dominant has two meanings: the dominant function (that of the fifth chord in the scale), or the dominant seven chord (which may or may not have a dominant function). Practically, most musicians do not use term 'dominant' when referring to the dominant 7 chord (aka, maj min 7 chord or simply 7 chord). Most often they'll just say 'C7' instead of 'C dominant 7'. Which is what I prefer, because I reserve the use of the word 'dominant' for the chords that function as dominants.

Your're obviously not referring to the dominant chord (i.e the fifth chord) because the dominant chord of a major key is always part of the scale. You're referring to the 7 chord based off of the tonic (in your example, or some other note general) which does not function as the dominant chord of the scale (it could be, however, functioning as a secondary dominant: C7 is the dominant chord from the key of F, and it can help you modulate to F). Whenever you have maj min 7 chord that isn't the fifth chord, it may be explained by theory in several ways (secondary dominant, tritone substitution, etc... I'm not into that stuff).

In 12 bar blues, all chords can be played with an added minor 7th and it doesn't sound wrong, and the only explanation I can give for the fourth being played dominant is that it just sounds cool. The point is, if it doesn't have a simple theoretical explanation, don't look for a complicated one.

So why do we use a flattened 7th in a major dominant chord? All dominant chords have flatted 7s that are part of the scale (for example in the key of C, G7 is the dominant and its 7th is F). You probably meant: why do whe play dom 7 chords that are not the fifths (functional dominants)? So again to summarize, it could be explained using theory (read about secondary dominants, modulation, tritone substitution...) or it can have no explanation at all. Some people like chicken with ice cream, why not? This is art, not math.


The flatted 7th is in the scale. You're just thinking about the wrong scale. The term "dominant" refers to the 5th note of a scale. In the case of C7, C is the 5th note of the F scale. The note Bb is in the F major scale.

  • In other words, it is in the C Mixolydian scale. ..
    – mey
    Commented Feb 5, 2015 at 19:23
  • @Mey C7 is the dominant of F major, not of C mixolydian.
    – phoog
    Commented Mar 5 at 0:48

The short answer is: it just is.

The longer answer is because something like "C7" is shorthand for a dominant seventh quality chord. In tonal music, this is arguably the most common type of seventh chord, so the shorthand C7 just assumes a flattened seventh for practicality's sake.

By "dominant-seventh" quality above, I mean the seventh chord built on the fifth scale degree. This will be a major triad with an added minor seventh (hence this chord is also sometimes called a "major-minor seventh," indicated a major triad with a minor seventh). So in F, C is the fifth scale degree, and building a seventh chord on C (in the key of F) will give you C, E, G, B-flat.

Thus C7 doesn't really suggest the key of C at all, it really veers more towards F. Once again, this is because an X7 chord (insert any note there you want) is a dominant seventh quality, meaning it's built on the fifth scale degree, meaning it alludes to a key a perfect fifth below its root.

In short, a C7 chord has nothing to do with a C scale, hence using "'THE REAL 7th' note of the scale" doesn't matter. Instead, standard chord labeling practice simply indicates that an X7 chord is a dominant seventh.

As for when this was adopted, I'm not sure. I would guess around the time of lead-sheet notation, but I really don't know.

Edit: For some recent related discussion, check out What does "dominant" mean in music?


The flat 7th is in the overtone series of the root note. For example, let's say you play an A7 dominant chord starting with the A at 440 Hz. The frequencies in the overtone series for the A are:

Frequency  Closest pitch
440 Hz     A
880 Hz     A
1320 Hz    E
1760 Hz    A
2200 Hz    C#
2640 Hz    E
3080 Hz    G
3520 Hz    A

Notice that A, C#, E, and G – the notes in the A7 chord – appear in the overtone series of A within 4 octaves. G#, the 7th in the AMaj7 chord, appears much, much later in the overtone series.

  • 2
    The 7th overtone isn't particularly well-represented by the minor 7th in well-tempered tuning, so for much of western music you can't apply this argumentation really well. Commented Nov 3, 2013 at 21:44

The notation developed that way due to what was used most often. In general in chord there are certain intervals that are perfected to construct harmony from. While the degrees preferred for harmony mostly line up the major scale they are not the same consent so comparing them is like apples and oranges.

The minor 7th make much more sense to use as a default 7th in notation due to it's importance in harmony and how much more it comes up.

Think of it this way as most introductory courses teach chords. In the Major scale when building 7th chords, only two of the seven 7th chords will have a major 7th. Built of the C Major scale that would be CMaj7 and FMaj7 only. The rest have minor 7ths including the dominant which is the fulcrum in functional harmony and uses the minor 7th along with the major third to better get you back to the tonic of whatever key you are in.

  • is there a book (or another source) stating that "the notation developed that way due to what was used more often" ? Commented Jul 28, 2016 at 14:33
  • It's pretty much stated in any theory book. Any good theory book will show you how the minor 7th plays a critical role in functional harmony and overwhelmingly is utilized over the major 7th when talking about harmony.
    – Dom
    Commented Jul 28, 2016 at 14:38
  • I already know the arguments related to functional harmony, dissonant sounds, constructions of the chords etc. I wanna get into the "correctness" of the notation. if someone says that we adopted the C7 with the 7th flattened cause it's the most often used, I would accept that. otherwise, I still don't have an answer for that (considering the notation itself, not the construction of the chords). do you understand me? Commented Jul 28, 2016 at 14:52
  • I don't think you are actually get what I'm saying. The notation we use to notate chord symbols developed from functional harmony and in functional harmony the minor 7th is the most used 7th even in more modern mindsets like jazz that's still true. We define the notation to reflect this and I'm not sue where this idea of "correctness" you have is coming from especially using the major scale as your argument as in this case it's completely unrelated. The chord symbols are the same no matter what scales you use.
    – Dom
    Commented Jul 28, 2016 at 14:58
  • @IsaacNogueira "Is there a book (or another source) stating that "the notation developed that way due to what was used more often"?" Check the answer I just added, I include references to a historical source from the development of chord symbol notation that speaks to precisely this rationale.
    – hopper
    Commented Jul 28, 2016 at 16:00

A dominant 7th is build from the dominant chord of the scale. It is easy to see why a maj7 and a dom7 is different and where the flattened 7 is coming from. Lets look at the Amaj scale, which is the easiest. Lets also extent it to the 13th degree

A B C# D E F# G# A B C# D E F#

The theory states that the chord build from the fifth degree is a major chord, and also the dominant, which in this case will be a E chord. The notes making up this E will be 5th, 7th and 9th degree of the Amaj scale, which will be E, G# and B. (this is the same notes on degrees 1, 3 and 5 of the Emaj scale).

If we build a dom7, (in this case an E7 chord) we need to add the note 7degrees from the E note, so in this case, it wil be the 11th degree of the Amaj scale, which is the D note.

A major 7th is build by taking the root, 3rd, 5th and 7th from the scale, so build a Emaj7, lets look at the Emaj scale

E F# G# A B C# D#

So, as you can see, the Emaj7 will have the notes E, G#, B and D#.

If you now look at the maj7 and dom7 chords that we have build, you'll see that E7 have a D note, which one semitone lower than the D# note we find in the Emaj7. This is where the theory comes from that a dom7 have a flattened 7.

This is the practise that I have used to make it really simple to understand the diffirence between a maj7, min7 and a dom7 chord. I hope this will make things a bit easier to understand


C 7 is not a chord built on a C Major scale, if you take a look at the scale, the Major 7 is (B natural) -

this chord could be : the dominant (chord built on the V step of a scale) of F Major (for almost all genres, starting from Baroque to modern times)

or : the I (first) chord of a composition/song that use modal scales or blues scales, as a matter of fact, blues music is a mistery, you can use both minor and major (pentatonic) scales and...get away with it !

in Classical theory, the "dominant" chord should resolve to a consonant chord, as the I (like C7 resolving (moving to) F Major)

in modern theory (beginning in the late 1800, with the Impressionists) this chord can be placed almost everywhere in the composition


The dominant chord has been commonly used in western music for a lot longer than any other 7th chords.

The V7-Imaj7 progression is used very often in jazz, however its roots are in the more classical V7-I cadence, which again has roots in the V-I perfect cadence.

The F in a G7 resolves directly to the E in a C chord. This was discovered early on, and made the dominant chord the status that you are referring to in your question. It is the first 7th chord to be commonly used.

In contrast, at the time, the major 7th chord sounded dissonant. The semitone clash of the major 7th and the root of the chord sounded unresolved to people at this time.

Every other 7th chord is more complex, intricate and dissonant than the dominant 7th chord. Perhaps this is why/how jazz musicians manage to alter 7th chords so much, and so much more than any other chord; by extensions: 9th, 11th and 13th chords; and alterations b5, #5, b9 and #9


When i took western theory and harmony at the com. coll. the first thing the teacher told us was,go to the Overtone series. So a dom.7th is because the 7th goes flat in the overtone series.Also he said ,if you look at the notes that go flat as the o.s. goes on,you naturally have a BLUES Scale ,with a flat 7,5,3..this opened my mind for Blues music.

  • Hello and welcome to the Music.SE site! Could you elaborate on your answer, and explain that the dominant 7th occurs in the harmonic series before a natural 7th? Also, to give a complete answer, could you address the issue raised about whether or not the dominant/flat 7th is in the scale? Thanks for sharing your expertise!
    – jdjazz
    Commented Jul 19, 2017 at 17:29

Lets see what exactly is a dominant seventh.

It a is a chord which instead of three notes with one of the notes being doubled we have four different notes.

So instead of having four notes being C-E-G-C we have C-E-G-B. The seventh chord is a tetrad (Triad but four notes instead of four)

Now you could build chords with this added note on any scale degree. The tonic being the exception as its seventh is both the leading tone of the scale and the seventh of a chord. So there is issues regarding the resolving of that note.

You ask then why is the Bb in the C dominant chord flattened then. because when you play that chord typically in a classical harmony you are not in C major. It is a dominant chord. It is build on the fifth note of the scale. The tonic in which this chord would operate is F and F major has a Bb.

  • Your 4th para. is about Cmajor 7, which is perfectly acceptable, and often used. Every note in a diatonic scale has 3 other notes which build on it to make another chord. Sometimes even more notes add on in a similar manner. This answer could cause confusion, although the last para. is correct.
    – Tim
    Commented Jul 29, 2016 at 6:08
  • Dv'd as it doesn't explain why properly.
    – Tim
    Commented Apr 3, 2021 at 17:48

"My point is: the 7th note (of the C major scale) is B (not B flat) * [C, D, E, F, G, A, B] *"

You are correct. There is no B flat in the C Major scale. But, that is NOT C7. C7, what I think you are asking about, is the FIFTH in the key of F. These 7th chords come from the fifth of the scale.

1, 2, 3, 4, 5 F, G, A, B, C

I tried to explain this yesterday in my post. When you say C7 we are talking about the fifth of a scale.

The formula for the C7 chord in the key of F is 1, 3, 5, flat 7 or C, E, G and B flat.

I think every post here explained your question.


C7 chord is part of the F major scale and it's the 5th numeral of the scale.


The formula for the C7 chord is not 135flat7, it’s the three intervals of major, minor, minor which is "M m m".

This results in a 135flat7 and starting is a C minor seventh. But when you build the chord starting at the fifth instead of the one there is a half step difference.

You can also see this phenomenon when building a map of keys as the harmonic distance between the notes is not proportional to it's interval distance but instead cyclical.

Specifically to WWHW ... half of the diatonic scale.

Get it? ... Diatonic meaning "two tonics".

The diatonic scale is WWHWWWH but when you're moving up fifths to the next key it's actually twice the distance ... WWHW * 2.

As you can see the extra W resulting in the name of the key two steps up.

For example, two keys up from C is D. Two keys up from D is E. Two keys up from B is F#, right? ... not F.

  • What is wrong with this answer such that it gets a downvote. What possible information would be needed to be rewarded? Commented May 16, 2018 at 3:56
  • 1
    There's a lot wrong with this explanation. The first line is misleading by calling a correct interpretation of it wrong and using a very nonstandard representation (1 - 3 - 5- b7, root, M3, P5, m7, Mm7, and Mmm are all equivalent). C minor 7th is typically intepreted as C minor chord with a minor 7th. 3rd paragraph is confusing because you've started to talk about keys instead of chord. Diatonic != two tonics. The root word is Dia not Di. The last 3 sentences are pretty much incorrect and what you are talking about is just the circle of 5ths. It has nothing to do with the question.
    – Dom
    Commented May 21, 2018 at 22:10

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