View the full lesson at Comparing the E Shape 7th Shapes | JustinGuitar
In the examples Justin shows of E-shape chords he mutes the fifth string. I get that for it to be a moveable shape that needs to happen, but it there a reason in theory why in the special case of an A chord using the E-shape the fifth string shouldnât be played? Or of using the fifth as the root and not playing the sixth?
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Iâm not sure if I understand correctly, so pardon me if Iâm not answering your question.
7th chords, which Justin calls âquadadsâ, are in essence 4 note chords: the root, some kind of 3rd, some kind of 5th and some kind of 7th. The E shape has the root note on the 6th string. In order to play a full barre chord, we need to play some notes more than once in order to cover all strings.
Depending on the type of chord, this can pose multiple problems:
1 - We are physically unable to fret a chord tone on every string because theyâre too far apart.
2 - Full quadad barre chords often donât sound that great, especially when the root note and the 3rd are on adjacent strings. Listen to the full chord shape he plays at the 2:15 mark in the video and compare it to the shape he teaches. (Remember the open G chord with a muted 5 string you probably learned? Same reason.)
3 - Some notes are more important than others. The 3rd and the 7th are the essential notes for quadads. The 5th doesnât add much value to the chord, so itâs often omitted. The root note is important too, but sometimes the bass player or the underlying harmony can take care of that.
Thatâs why Justin teaches so called mini shapes, where some strings / notes arenât played. We can even play 7th chords with just a 3rd and a 7th. Smaller shapes often sound better!
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The open A string is of course the root, an identical note to 6th string at fret 5.
It is the root and can be played as such - instead of 6th string.
It will have a slightly different timbre and it is up to you and your ears to determine if you want that sound. If you want fretting hand muting options - say for a staccato rhythm - the open 5th string does not allow for that so easily.
I hope that helps.
Cheers 
| Richard | JustinGuitar Approved Teacher, Official Guide & Moderator
Thanks Richard thatâs pretty much what I thought. If Justin remakes this video might be worth a passing mention as I think it helps to underline the point about understanding the function of each note rather than just following chord shapes.
I donât have my guitar with me (on hols) so I canât try it, but would you ever play the A on both the fifth and sixth strings as part of the chord?
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If you wanted the really fat, bassy sound that two equivalent bass notes brings, yes, thereâs no reason not to. Be guided by âif it sounds good it is goodâ.
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For 7 chords, the 7b is not in the scale, so how come it works as a note in a chord? for example in C7, we play C,E,G,Bb. Bb isnât in the scale of C, so how come this works?
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It is in the Mixolydian Scale. The major scale with a flat 7 Giving the major scale a bit of a bluesy feel. This is why a lot of Blues uses dominant 7 chords over Major chords
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As @stitch said, the blues is a language that breaks many of the rules. Itâs common to have a 1-4-5 progression entirely with dominant 7th chords:
C7 - F7 - G7
or G7 - C7 - D7
or F7 - Bb7 - C7
âŚ
Dissonance is one of the key elements of the blues.
In a non-blues context, a C7 complies with the rules when it functions as a dominant V7 chord. In this case, C7 would be the V7 in the key of F. The note Bb is found in the F major scale, so all good here.
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Yes it is.
Because the one and only chord of al lseven chords in a key that becomes a â7thâ when extended beyond the triad is the 5 chord. It becomes a dominant 7 or V7.
The two other major chords in any key (the 1 and the 4 chords) become major 7 chords (not dominant 7 chords).
In the key of C âŚ
The 1 chord (tonic) extended becomes C major 7:
The 4 chord extended becomes F major 7:
The 5 chord extended becomes G7:
If youâre playing a C7 chord and are trying to figure out the key it fits within so it is a âchord-in-the-keyâ (a diatonic chord) you now know it must the be the 5 chord of something. Count backwards from C â B â A â G â F.
C7 is the V7 chord in the key of F. And the F major scale does contain the note Bb (which is a chord tone of C7).
Further, as @stitch and @Jeff mention, 7 chords in certain musical contexts (blues for example) are played because they sound good and they bend / break the rules.
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@Richard_close2u This is all true but the lesson is on E shaped 7 chords which replaces the second Root note (octave) with a b7. The example given ask why the Bb worked in the E shaped C 7 when itâs not in the C major scale. The simple answer is it is constructed using the mixolydian mode. R 3 5 b7
Rick, I think youâre doing @zacreh a disservice here to be frank. This is grade 6 PMT. Modes, including mixolydian, are not even introduced until grade 7 PMT.
In terms of understanding why and how a dominant 7 chord can contain a b7 - a note seemingly not in the key of the root note of the dominant chord - the chord shape is irrelevant. The same analysis and explanation would apply to all five of the CAGED shapes explored in grade 6 PMT.
Whatever the major scale root note is, that note will not have a dominant 7 chord built on it. Because the I chord, the tonic chord, in each and every major key extends to become a major 7 chord.
It is the V and only the V chord that extends to become a dominant 7. Because when the notes are stacked in thirds, from the 5th scale degree, as shown in the diagram I made, the fourth note of the quadad is a flat 7 when using the root note of the V chord as the start point.
The question asked âŚ
⌠could equally be asked of minor 7 chords âŚ
the b3 and the b7 are not in the scale, so how come they work as notes in a chord?
And the answer is the same. When looking at the chords within a major key, if a chord is minor, its root note is not the root note of the key. It is not the tonic chord. It must be a chord built on one of the other scale degrees. Minor type chords are built on the 2nd, 3rd and 6th scale degrees.
It works with m7b5 aswell.
neither the b3 nor the b5 nor the b7 are in the scale, so how come they work as notes in a chord?
Because they are in a chord that is not built on the root note of the key. It is not the tonic chord. Rather, for diminished type chords alone, they are built on the 7th scale degree.
The CAGED shape does not enter into the thinking.
The fact that all four â7â types of chord are shown and that they are derived from the concept of an E-shape major chord is simply a visual learning aid.
The lesson is not saying that E major (the chord) is the tonic chord, that the chords being studied are in the key of E major (the key centre).
So when looking at a C7 (as @zacreh gives the example of) it is a blind alley and incorrect to think that C major is the tonic chord or to think that C major is the key centre from which a C7 chord is derived.
It is merely useful as a method of learning to compare and contrast and note how the changing of one note can lead to the many types of â7â chord being taught.
But the very fact that the notes are changing means most of those chords (not the major 7 necessarily) change the chord family and the key centre that the â7â chords belong to.
C major chord â key of C major (tonic chord as a triad)
C major 7 chord â key of C major also (tonic chord extended to a quadad) or key or key of G major (IV7 chord)
C minor 7 chord â key of Bb major (ii7 chord) or Ab major (iii7 chord) or Eb major (vi7 chord).
C minor 7 b5 â key of Db major (vii7 chord)
All of that should be within the scope of PMT up to grade 6.
I donât disagree with you very often Richard but I think You are doing a disservice by over complicating an answer to a very simple question.
It is also a blind alley and incorrect to think the chord is the 5th of a key. Theory teaches major chords are made of stacked 3rd of a Scale. R 3rd 5th. to make a dominant 7 chord you add a Flat 7 which is not in the Major Scale but it is in the mixolydian which is also built off the 5th of the major scale. Sometime the simplest answer is the easiest to understand.
Rick, I concede, I have over complicated the issue. Very much so. I had a thought nagging me to keep it simple and I ignored it.
Your post had brevity, and is good if responding to a more advanced learner.
But I hold to my points that the chord shape is irrelevant and mention of mixolydian is beyond the scope of a grade 6 theory question.
To keep it simple, to put simply, if you are playing C7, you are not in the key of C.
There are exceptions and anomalies. But that is the basics of it.