Our focus in this lesson is on the b7-chord in the major key.
The major key has seven unique chords:
The 1-chord:
The 2-chord:
The 3-chord:
The 4-chord:
The 5-chord:
The 6-chord:
The 7-chord:
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Attention: All the references above are given in the key of C major.
But in so many occasions, the chord of the seventh tone of the major scale (aka – “the 7-chord”) is excluded from the list and this is because it is the most dissonant chord in the major key and I’ll tell you why in the next segment.
The 7-chord: The Most Dissonant Chord In The Major Key
The 7-chord in the key of C major:
…is the B half-diminished seventh chord:
A breakdown of the 7-chord into intervals:
B-D:
B-F:
B-A:
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…shows the particular interval behind the dissonance of the 7-chord and that’s the tritone — “B-F”:
All chords with the “tritone” are highly dissonant (or unpleasant) when played and the 7-chord is no exception.
Beyond The Seventh Chord: Other Intolerable Dissonances Of The 7-chord
Interestingly, the tritone is NOT all there is to the 7-chord in the major key. As we extend the 7-chord by adding other chord tones (known as extensions) to it, we’ll come across other intolerable dissonances.
“Kindly Give Me Your Undivided Attention…”
The extensions of the 7-chord in the key of C major are:
The ninth (which is C):
The eleventh (which is E):
The thirteenth (which is G):
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Adding the ninth to the B half-diminished seventh chord:
The ninth (which is C):
The B half-diminished seventh chord:
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…produces the B half-diminished seventh [flat ninth] chord:
…which is a very unpleasant chord with an intolerable degree of dissonance.
In the B half-diminished seventh [flat ninth] chord:
…the root is also clashing with the ninth tone to produce the minor ninth interval — the most dissonant interval in tonal music — which has this degree of unpleasantness that cannot be appreciated.
Even if other extensions (like the eleventh and thirteenth are added) it doesn’t get any better:
With the eleventh:
With the thirteenth:
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“So, Back To Our Conversation On The 7-chord…”
You’ve clearly seen why the 7-chord is usually excluded in the major key.
Submission: Music scholars are familiar with other cases where the 7-chord is considered as an incomplete 5-chord and we’ll learn more about that in a subsequent lesson.
Introducing: The b7-chord In The Major Key
Did it escape your notice that the dissonance of the 7-chord is basically coming from its root.
In the first example, the root and the fifth tone (“B-F”) forms a dissonant interval.
In the second example, the root and the ninth tone (“B-C”) forms an intolerably dissonant interval.
I’ll be showing you what to do to the root of the 7-chord in this segment.
Here’s What To Do With The Root Of The 7-chord
The root of the 7-chord in the key of C major:
…is B:
Due to its clash (formation of an unpleasant interval) with the fifth and ninth chord tones, we can go ahead to chromatically modify it and this entails lowering the root of the 7-chord by a half-step.
So, lowering the root of the 7-chord in the key of C major (which is B):
…by a half-step (to Bb):
…produces a set of chromatic chords (chords that are foreign to the key of C major) that are a lot more pleasant.
The Chromatic Nature Of The b7-chord
Lowering the root of the 7-chord produces b7-chord varieties for every single 7-chord and I’ll love you to check them out.
“Here You Are…”
For the B diminished triad (the 7-chord), there’s the Bb major triad (the b7-chord):
The B diminished triad (the 7-chord):
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The Bb major triad (the b7-chord):
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For the B half-diminished seventh chord (the 7-chord), there’s the Bb major seventh chord (the b7-chord):
The B half-diminished seventh (the 7-chord):
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The Bb major seventh chord (the b7-chord):
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For the B half-diminished seventh [flat ninth] chord (the 7-chord ), there’s the Bb major ninth chord (the b7-chord):
The B half-diminished seventh [flat ninth] chord (the 7-chord):
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The Bb major ninth chord (the b7-chord):
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We could go on and on.
Attention: Between the diminished quality of the 7-chord and the major quality of the b7-chord, you already can tell that the 7-chord is unpleasant while the b7-chord sounds pleasant.
Final Words
Keep in mind that the b7-chord is not related to the 7 chord in anyway. There are still structural and functional differences between both chords: for example, the former is chromatic while the latter is diatonic.
We’ll look at the characteristic differences between both chords in a subsequent lesson. Until then, keep enjoying your b7-chord in the major key.
Thank you for your time.
Chuku Onyemachi
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