Why does Justin call the 7th chord in the key of C half diminished?

[MAT1953]

Richard @Richard_close2u
Here is your starter for ten in your new role.

The query is about the description of half diminished and diminished triad chords.
Earlier in the course, Module 4.1, when Justin introduces triads and when you build a chord off the 7th degree of the scale and when analysed you get 1 b3 b5 which Justin describes as a diminished triad chord.

However, jump forward in Module 5.3 and the lesson on Dorian and Phrygian Modes at about 40sec in Justin says chords in the key of the C major gives you the following chords,
I am assuming he is talking about triads.
C Dm Em F G Am but describes B as half diminished.

Is this not a contradiction of what was outlined before,

Michael

[mathsjunky]

Here’s my thoughts … Richard can correct me

A diminished triad contains the 1, b3 and b5.
When you add a 7th then it becomes a half-diminished chord if you add a minor 7, or a fully diminished chord if you flatten the minor 7 (bb7).
A half-diminished chord is by definition not a triad.

[MAT1953]

Paul @mathsjunky

I agree with what you are saying about 7th Chords being either half diminished (b7) or diminished. (bb7).

But listening to what Justin says in the video about it being half diminished, he is in my view clearly talking about triads in a major key.

I am sure Richard will advise but I think that it may be a slip of the tongue.

Michael

[sclay]

In the practical world, the m7b5 is favoured over the diminished triad. It sounds better, is more versatile, and is a diatonic chord of the Major Scale.
I think Justin is just reflecting this reality, as do most teachers I’ve come across. Its simply a matter of perspective, complexity, and use, rather than any contradiction.

Cheers, Shane

[Richard_close2u]

@MAT1953

Here is your starter for ten in your new role.

Thanks Michael.

The query is about the description of half diminished and diminished triad chords.

Technically - only ‘diminished’ is a triad. Half diminished, fully diminished, dim7, m7b5 (there are several ways to name them) are not triads but extensions to what Justin calls a ‘quadad’. I’m sure you know that.

… Module 4.1 … build a chord off the 7th degree of the scale and when analysed you get 1 b3 b5 … a diminished triad chord.

Yes. All good so far.

… Module 5.3 … Justin says chords in the key of the C major gives … C Dm Em F G Am but describes B as half diminished.

I have checked - yes he does.

I am assuming he is talking about triads.

It seems he is. If he meant other than triads he would have named the first six as Cmaj7, Dm7, Em7, Fmaj7, G7 and Am7. But he then speaks with an inconsistency by making mention of B half diminished. That is not a triad but a quadad. I’m sure it was no more than a slip of the tongue.

The reason, which I’m guessing at, is perhaps due to the fact that in real-life usage, diminished triads are seldom used in triad form. Instead, they are mostly played in extended form as half diminished chords. And Justin would probably call the seventh chord half diminished in general musical conversation if speaking about chords in a key.

Is this not a contradiction of what was outlined before?

In as much as Justin spoke a little beyond the triad focus it is misplaced slightly. But not incorrect not contradictory. I think he simply slipped into common parlance which meant he coloured slightly outside the lines of the picture the lesson / module is there to paint.

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@mathsjunky and @sclay make perfectly legitimate comments.

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You have got me started though.

Most of the lessons in PMT have been looking at the major scale. Just prior to this lesson (on Dorian and Phrygian) is the lesson on Harmonic Minor. And that too may have influenced Justin comment. If he filmed them in order, and at the same time, his thoughts, off camera, may also have been concentrated on the diatonic chords of the harmonic scale. And, crucially for your question and the discussion of diminished chords, when a quadad is built from the seventh scale degree of Harmonic Minor, it gives a fully diminished chord. Perhaps Justin name checked half diminished as a contrast to the fully diminished chord that had been in his thoughts a few minutes before, but which didn’t make it to the finished edit of a lesson. Again, I am guessing.

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Here are two diagrams depicting two types of B diminished chord.
The first is B half diminished derived from the C major scale.
The second if B fully diminished derived from the C harmonic minor scale.

B half diminished (Bm7b5)

B fully diminished (Bdim7)

Both contain a diminished triad.
1, b3, b5
B, D, F

The crucial distinction, and the rationale behind naming them as half / full stems from the interval from root to the ‘7th’.
The note span of B half diminished from Root to b7th is 10 semitones = minor 7th.
The note span of B fully diminished from Root to bb7th is 9 semitones = diminished 7th.

The fully diminished chord contains a ‘7th’ two semitones below the major 7th. It takes the action of ‘double-flat’ to reduce the note span from the 11 semitones of a major 7th to reach the 9 semitones of a diminished 7th. This interval is described as ‘fully’ diminished.

In comparison, the half diminished chord contains a ‘7th’ just one semitone below the major 7th. The contraction in its total span from 11 to 10 semitones is only half the contraction that gives a fully diminished interval. Hence the chord is called ‘half diminished’.

Bm7b5 = B half diminished = B

Bdim7 = B fully diminished = B

[MAT1953]

Thanks Richard @Richard_close2u

As always, a comprehensive and easy to understand explanation.

I must have really been paying attention to the lesson to pick that up on it.

The diminished 7th chord construction built on minor thirds is interesting– don’t think Justin has explained it in any of the PMT lessons so far but I could be wrong about that.

Thanks again.

Michael

PS you got your 10 marks so here are your four questions on …………. worth five points each. It reminds me of highbrow quiz programme.

[Richard_close2u]

@MAT1953

The diminished 7th chord construction built on minor thirds is interesting– don’t think Justin has explained it in any of the PMT lessons

That’s my own additional information. I like to explore connectikns, patterns, sequences etc.

The interior intervals of triads are fascinating.
Major 3rd = 4 semitones.
Minor 3rd = 3 semitones.
Chords are constructed by stacking 3rds.

Any major triad contains a major 3rd (from root to 3) then a minor 3rd from 3 to 5.
Any minor triad contains a minor 3rd (from root to b3) then a major 3rd *from 3 to 5).
The interior intervals are inverted.
This means the total interval span of both major and minor triads is the sum of one major 3rd plus one minor 3rd.
4 semitones llus 3 semitones = 7 semitones.
7 semitones = a perfect 5th.
In both major and minor triads, from Root to 5th is the interval of a perfect 5th.
Connect that to power chords … when you remove the 3rd entirely, you have only Root and 5th. That explains why power chords are neither major nor minor and can substitute for either one.
Connect it to sus2 and sus4 chords … when you remove the 3rd and replace with a 2nd or a 4th, you have only Root and 5th and one other note instead of the 3rd. That explains why sus chords are neither major nor minor and can be played alongside either one.

[sclay]

@MAT1953

The diminished 7th chord construction built on minor thirds is interesting– don’t think Justin has explained it in any of the PMT lessons so far but I could be wrong about that.

Interesting it is. It’s pretty much a ‘unique’ chord structure.
Because dim7s are all stacked minor 3rds - ie, equidistant intervals - the same dim7 shape will give you four dim7 chords for the price of one; with each note being able to function as the root.

Slide it up and down the neck 3 frets, and you get the same notes, in different inversions.
So there’s only really 3 shapes on the whole guitar, and thats due to the B string tuning shift.

Cheers, Shane

[telemann1]

@sclay

the same dim7 shape will give you four dim7 chords for the price of one

Yes indeed. I learned piano for a while and the dim7 was a really easy one. You only had to learn three shapes and you could play any inversion, anywhere on the keyboard.

[telemann1]

@Richard_close2u

Connect that to power chords … when you remove the 3rd entirely, you have only Root and 5th. That explains why power chords are neither major nor minor and can substitute for either one.

And you can go the other way. Remove the 5th and just play the root, third and seventh which are the main “essentials” of the chord. Discovering shell voicings was a huge eye-opener for me.

[Richard_close2u]

@telemann1

Remove the 5th and just play the root, third and seventh which are the main “essentials” of the chord.

Yes - from a 7th extension the 5th becomes dispensable.
That is also true for further extensions to 9th, 11th, 13th etc. And with those further extensions, so long as the 1, 3 and b7 are present, the 5th is dispensable, the 9th is dispensable from an 11th, the 9th and 11th are dispensable from a 13th.

[telemann1]

@Richard_close2u

1, 3 and b7 are present, the 5th is dispensable

And if you have a bass player you can even drop the 1 (in fact, he would probably prefer that).

[MAT1953]

Interesting Richard @Richard_close2u
I think it might take me a while to work through this.
Michael

[MAT1953]

Shane @sclay
Another interesting thing to follow up.
Michael

[mathsjunky]

It’s also true of Augmented triads - 1, 3, #5. These are a major 3rd apart so any note in the triad can be considered the root and they repeat every 4 frets.

[Richard_close2u]

@MAT1953

Shane @sclay
Another interesting thing to follow up.

See if this helps you understand the concept Shane explained.
The Note Circle shows that there are 12 semitones in total.
The interval of a minor third is 3 semitones.
Therefore, four successive minor thirds must total 12 semitones.
If you track the notes of a fully diminished chord from Root to b3, to b5 to bb7 to Root again, four successive minor thirds are within.

The diagram below shows this for Bdim7, Ddim7, Fdim7 and Abdim7.
Bdim7 follows from the posts above. once it is chosen, the other three follow naturally as they are the notes found inside Bdim7. Each in turn becoems the Root of the next dim7 chord.

Here are the four dim7 chords using the same grip on A, D, G & B strings. They are all spaced at a distance of three frets (a minor third) from each other.

[simon_plays_bass]

@telemann1

@Richard_close2u

1, 3 and b7 are present, the 5th is dispensable

And if you have a bass player you can even drop the 1 (in fact, he would probably prefer that).

Bass player here (a clue in my user name perhaps ). Dropping the 5th interested me. I suspect it is the first chord tone (other than the 1) taught by most bass teachers. I think this is probably due to where it sits on the fretboard (both upper and lower) which makes it easy to get to, and because it usually sounds good and hardly ever bad. I agree the 3rd is more important than the 5th for outlining harmony (which I consider one of the 2 main roles of a bass player), but 1, 5 may be the most common chord tones played by many bass players.

I was going to say I use the 3rd and 5th way more than the 7th. On second thoughts, I use the flat 7th a lot without really thinking about it, as it sits nicely in a minor pentatonic shape. The location of the upper 5th on the fretboard does make for an easy way to the flat 7th.

To @telemann1 ‘s comment about a bass player preferring guitarists to stay away from the 1 (and other things the guitar teacher said in the video related to the bass), it kicked of a whole new set of thoughts. These are are probably best left for a different topic though .

[mathsjunky]

The 5th is the bane of my life when transcribing! You often get it ‘for free’ in a mix as it’s a strong and stable harmonic. It’s a very common issue for some people hearing the fifth of a note instead of the note itself - and typically the 5th will sound ‘good’ so there’s a temptation to think it’s the correct note. I do it so often that if I’m ever not 100% sure about a note I’m transcribing I will try the note a 4th down (the note whose fifth is the note I think I can hear) and it’s often correct.

[telemann1]

@simon_plays_bass

comment about a bass player preferring guitarists to stay away from the 1

I got this from a Tim Lerch video lesson I looked at a while ago. He was teaching a way of interspersing a short lead melody with a two note “outline” to define the chord. He said if you have a bass player you can leave out the root because they will take care of that part of the chord, and you only need to worry about playing the 3rd and 7th notes. So, it may be more of a jazz concept.

I was assuming it was because the bass player will be doing something clever and didn’t want you to be getting in his way with notes that may clash.