# Topic: why is c7 a semi?

1. ## why is c7 a semi?

A C7 Chord means a normal chord + a seventh degree to the root, which is actually:

Code:
`0+4+3+(10)`
On the white keys of a keyboard the 'seventh' from C is visually a B, thats +11 semis.
But for some reason a C7 chord has a fourth degree of Bb, thats only +10 semis.
Is this only true for the C chord, or why is that?
Why is the seventh degree of a C7 chord a B-flat and not a B?
I really have a very hard time to integrate that.

2. ## Re: why is c7 a semi?

It's the jazzers and rockers who decided to give it the wrong name. For a major 7th chord (i.e. the C chord with a B natural) they tend to put a little triangle after the C (although there are several conflicting notations). It does apply to every chord - so B7 has an A at the top, Bb7 has and Ab, A7 has a G, etc.

This is what happens when you start trying to talk about chords without any reference to key

3. ## Re: why is c7 a semi?

BuddhaMaster:

The natural seventh (the 7th tone of the diatonic scale) in C Major is, as you stated, "B."
But, ANY major chord can also have a MINOR 7th above its root. In this case the "B"
would be lowered 1/2 tone (or a semitone) to Bb. Major chords with a lowered
7th are normally called "DOMINANT 7ths." They resolve to a chord a "fourth" above
(or a 5th below).

This explanation is not comprehensive, but you can read about "scale tones"
that are a 7th above any note (major and minor 7ths) in an elementary music
theory book. This will also give you insight to many other musical tools that you
can use in your composing tool box............

Hope this helps a little.

Jack

4. ## Re: why is c7 a semi?

and of course, the language you speak also alters the way chords are marked.

for example, for a chord to be a "dominant 7th", in French, we marked it with the name of the chord (C = "do"), then a "7", but with a little "+" beneath the "7". This made it clear it was a dominant 7th chord. (if I recall correctly, the "+" indicates that the 3rd of the chord is the leading tone... generally speaking, the lowest number in a chiffrage indicates the mediant of the chord. here, the lowest number is simply replaced with the "+" which means the leading tone).

The way I was taught, chord analysis depends entirely upon the key in which the fragment being analyzed is.

So "in the key of C", a C7 chord WOULD have a B natural, as the note "B" in the key of C is the leading tone, and is a natural.

5. ## Re: why is c7 a semi?

I think BuddhaMaster wants to know why the "B" (natural 7th in the key of C) has
changed to a Bb. It's because the chord is not a MAJOR 7th CHORD, it is a DOMINANT
7th CHORD which resolves "normally" to an F Major/Minor chord.

A "C" DOMINANT 7th CHORD has a major triad (3 notes) with MINOR 7th (Bb) on top.

Once again, an elementary theory book would present this material sequentially which
would make this Major 7th, Minor 7th usage a little more clear.

Jack

6. ## Re: why is c7 a semi?

I was explaining that depending on the type of analysis you were taught, it might NOT be a flattened 7th.

For example, as I was taught, in the key of C, a C7 would NOT have a flattened 7, and would most certainly not be called a "dominant 7th" unless there was a modulation. The way I was taught, (French system) there is only one dominant 7th: on the V. Anything else is a diatonic 7th, which depends on the numerical function. Dominant 7ths only exist in one place: on a dominant. In the key of C, C is most definitely not a dominant.

Two different ways of looking at it. French analysis seems to rely entirely on the positional function of a chord within a key.

7. ## Re: why is c7 a semi?

My explanation of the dominant 7th was not related to the key of C per se, it was just
to demonstrate that a major triad with a FLATTED seventh is called a dominant 7th
(built on the fifth degree of a related key). Therefore, ANY dominant 7th SHOWS MOVEMENT, whether it is in the home key (back to the tonic) or as a modulatory instrument (to another key). The dominant 7th, regardless of key association, must MOVE. It is not a static chord. It must
resolve. It normally resolves to a chord that is a diatonic fourth ABOVE or a diatonic
fifth BELOW.

BuddhaMaster: Are you understanding any of this? We are having fun analyzing
our different theory systems, but the main reason we are doing this is to possibly
help you. Are we accomplishing that goal? Do you understand the reason why the
7th step of a scale can either be the natural 7th (1 semitone away from 8) or a 7th
that is two semitones away from the tonic (8th step)?

A reply would help us in assisting you.

Jack

8. ## Re: why is c7 a semi?

Put simply, flattening the 7th signals a move from the C to the F scale. A modulation. The change might be fleeting. In both jazz and classical harmony there is often a continuous ambiguity of key. The dominant 7th may lead to F, or just to another dominant chord with F in it somewhere. The sense of the musical idea finally arriving at a destination chord can be delayed almost to the end of a piece. Why bother? It is the interest created on the progression's journey which allows larger, more complex musical structures. Can you imagine a symphony with notes from one key only?

9. ## Re: why is c7 a semi?

Can't imagine that. A composition student at the Manhattan School of Music in New York knew a famous composer and when the composer looked at some of his music, he stated, "If you only knew how to modulate, you would someday be a famous composer."

That's the power that modulation injects into composition. Without it, your music tends
to be static and that leads to lack of interest or............death.

Jack

10. ## Re: why is c7 a semi?

Not sure where this is coming from but ALL the books I have state that C7 is C, E, G and B flat. If its a B natural then the chord is C major 7, if the chord is C minor, C, E flat, G, B flat the chord is C min 7. If the chord is C, E flat, G, B natural the chord is named C min major 7.

The B flat occurs because the C7 chord is the four part chord based on the 5th note in the scale of F. The same occurs in every key. It is correctly called the dominant seventh.

The method of naming chords as shown above is, as far as I understand, correct. C7 is never a chord with B natural, this is always C maj 7. Most DAWs will interpret chords and use this system. Look at www.gootar.com/piano/ and you will see it in action. Highlight the notes in a chord and the name is shown, it even works for really weird chords.

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