The Big Deal Of Chord Theory

The logic and process of what we're doing is far more important than the actual grips themselves!

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Why is the 5th missing in the “standard” C7 grip?


Hello @cloudynerd and welcome to the community. Feel free to pop in to the Community Hub and introduce yourself there. Community Hub - JustinGuitar Community

That is a great question. You may be surprised to know it is also a common one. You may be surprised at the answer too.

Fundamentally a chord needs three notes to be called a chord.
Three notes makes a triad at the simplest level.
The way that chords are constructed at the simple level is by stacking notes from a major scale in thirds.
Choose a note, miss a note, choose another note, miss a note, choose another note.

Let’s look at the G major scale.
G, A, B, C, D, E, F#
1, 2, 3, 4, 5, 6, 7

Take the notes 1, 3 & 5 to get a G major chord.
G major = G, B, D
All major chords, if written in their simplest triad form take the form 1, 3, 5.
For minor chords, the middle of those notes, the 3, is flattened so they have the form 1, b3, 5.

Major = 1, 3, 5
Minor = 1, b3, 5

When played as chords across more than three strings - which you meet immediately when learning your first open chords, you unwittingly get introduced to the concept that some or all of these notes can be repeated within the chord and may appear in different orders. For example, an open C major chord on five strings has the notes C, E, G, C, E - 1, 3, 5, 1, 3.

These ‘3-note chords’ can be made more complex by continuing to stack notes in thirds. An extension if what we saw above to include a further note will extend the G major chord thus:
G, A, B, C, D, E, F#
1, 2, 3, 4, 5, 6, 7

G maj7 = G, B, D, F# = 1, 3, 5, 7

It is now worth mentioning that all maj7 chords contain the 7th scale degree from the major scale that is their source.
Dominant 7 chords vary by having the same 1, 3, 5 but the 7 is flattened.
G maj7 = 1, 3, 5, 7
G7 = 1, 3, 5, b7

Now we have reached the dominant 7 chord we can start to address your question.

Within a dominant 7 chord, certain notes are indispensable.
The 1 must be present. It is the root and defines the chord. If the guitar is not playing it the bass or the keyboards or someone must be playing it. Period.
The 3 must be present. The 3rd scale degree determines the character of a chord - whether it be a major type (with a natural 3rd) or a minor type (with a flat 3rd). Dominant 7 chords are major type chords.
The b7 must be present. Without some sort of 7th we would not have a 7th type of chord. And it must be a flat 7th (to be dominant) not a natural 7th.
In all of this illustrious company some notes can be swamped, pushed aside, overlooked. They become optional extras. And of the four note dominant 7 chords, the 5 is the one that, sadly for it, can be discarded. It has no significant functional purpose with the structure and sound of a dominant 7.
Hence, C7 as a chord played in open position can comprise only the root, the 3 and the b7. Sorry Mr 5 but you’re not needed.
Hope that makes sense.

Cheers :blush:
| Richard_close2u | JustinGuitar Official Guide & Moderator


Thanks for the explanation. Makes sense. And it also sounds right, but always good to know some more of the background.

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Thanks for that explanation made a lot of jogical sense to me, much appreciated!

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A great lesson his one and the “homework” is a pretty good test of understanding 7th chords.

As there is more than one solution to turn an open dominant 7th chord into a major 7th chord, I arrived at the conclusion that the 5th can be left out of these ones, too. I found a string 5 root grip like that which is pretty comfortable to play.

Regarding the possible solutions, shall we stick to the general shape of the dominant chords in this exercise (i.e. keeping the root note on the same string), or can we examine whatever we find and check how “playable” they are?

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I’m wondering (in a gestalt kind of way) about the guitar player’s appreciation of the way chords are changed based on player experience. For example, a C7 chord can be seen as “adding a flattened 7th”, OR “adding a note that’s a tone below the root note”. Is one more likely to be used at a particular junction along the guitar journey? Or is there a point, as Justin says frequently, where you don’t think about it?

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It isn’t really clear what you’re asking here. Both are the same. Either can be used. A b7th is precisely one tone below a root whichever way you choose to describe it.

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My question wasn’t really about chord theory, but more about how the theory is learned. For example, when I first got into making beer, I had a rudimentary idea that somehow yeast made alcohol. (Put your fingers here for C7). Then I made beer with a boil kettle, mash tun, hydrometer, thermometer, siphon, immersion chiller, and numerous texts. (The dominant 7 chord has an added b7. See how this works with other chords.) Now I focus mainly on experimenting and making beers that I think taste good. (Your finger knows to add that b7 when needed, but you don’t think about the theory when you do it.) I hope this makes sense.

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When Justin first introduces dominant 7th chords in the beginner grades, it’s more about the grips and less about theory.

However, if you take the practical music theory courses, eventually you ought to know the functions (root, third, fifth, seventh, etc.) in a given chord grip. Of course, it takes time to get to that level, but so does everything that involves learning something new.

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I came here looking for the answer to that very question - thanks for the great answer.
Out of interest I fooled around trying to add one by using my third finger to mute the 5th string and hold the 3rd fret of the 6th string (for C7). It’s similar but doesn’t sound great.

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By moving your 3rd finger across to the 6th string and muting the 5th in a regular C major chord you have created a C/G (C over G). A C chord with G in the bass. An inversion. The G note is the ‘5’ in the C major chord
C = 1, 3, 5 = C, E, G

If you do similar starting from a C7 chord your bass note becomes the ‘5’ note and you will have the notes in this order:

G, E, Bb, C, E = 5, 3, b7, 1, 3

It has the 5 as the bass note and may be the reason you don’t like its sound.

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