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Music Theory Made Simple #43: Seventh Chords

stevel

Member
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15,132
We've learned how to build Tertian Triads (3 note chords, whose chord members are stacked in 3rds, or every other note).

Seventh Chords (7th henceforth) are also Tertian chords. We could say they're Tertian Tetrads. They are, but no one usually says that. So we just say 7th Chord and it's assumed they are 4 note chords (note: all 4 notes aren't always played, and we'll get into that later, so for now assume all 4 notes are going to be present for the purposes of naming and calculation, etc.).

So, they're Tertian 4-note chords, so that just means you stack up 4 "every other letter" notes.

Starting on A this would be A-C-E-G.

In case you missed that,

A B C D E F G A

See - every other letter.

If we count A as 1, then C is 3, E is 5, and G is 7 - the 7th, hence the name of this family of chords. Also, like triads, the names of the Chord Members follow the same pattern:

Root, 3rd, 5th, 7th.

A = Root
C = 3rd
E = 5th
G = 7th

Now would be a good time to practice 4 note Tertian stacks - whenever and wherever you get the chance:

A-C-E-G; B-D-F-A; C-E-G-B; D-F-A-C; E-G-B-D; F-A-C-E; G-B-D-F

and also

A-C-E-G; C-E-G-B; E-G-B-D; G-B-D-F; B-D-F-A; D-F-A-C; F-A-C-E

Practice them over under sideways down until you know them cold.

You may recall that there are only 4 types of Triad: Major, Minor, Augmented, and Diminished.

3 of these are found in Diatonic Keys. The 4th, Augmented, was really a chord that was made through chromatic alteration but is often explained by the possibility of creating it in Harmonic Minor (as III+, and that does provide a "complete" set).

Originally, 7th chords were done the same way: They were made from the notes of the Key (or even earlier, mode). As such, there are five (5) traditional types:

Major 7th
Dominant 7th
Minor 7th
Half-Diminished 7th
Fully-Diminished 7th

These were all they used in the olden days, or, shall we say, had "official" names for. Later, some other forms came into use, and in contemporary popular music even more forms were used. Patience grasshopper, we'll get to those. Let's stick with these 5 for now.

Now, the naming system befuddles a lot of people, but here's how the Classical Analysts do it:

There are two parts to a 7th chord: The Triad part, and the 7th Interval. Remember back when we were talking about Triads and I said there were 3 intervals: Root to 3rd, 3rd to 5th, and Root to 5th, but as a shortcut you only needed to know two of them because the remaining interval had to be a certain type of the other 2 were certain types? Well. a 7th chord has the following:

R-3, 3-5, 5-7, R-5, 3-7, R-7.

That's a lot of junk to figure out! You can, and there is some exclusive intervals, but man, that's too much to remember.

So what they did, since they had already worked out all this stuff for Triads, was realize that if you knew the Triad, and then the interval from the Root to the 7th, that's all you needed. And since you already know your Triads (you do, don't you?) all you really have to figure out is the 7th.

Ready for Brain Freeze: Remember the Intervals lessons? Yes, this is why you need them! Go back and learn them if you don't know them!!!!

Let's start at the top:

Major 7th Chord.

A Major 7th Chord consists of a Major Triad, and the Interval of a Major 7th from the Root to the 7th.

So we'd call this a "Major-Major 7th"

Major Triad + Major 7th.

C-E-G + C-B = C-E-G-B

You recall of course that those Intervals that can be Major or Minor, such as 2nds, 3rds, 6ths, and 7ths are all Major in a Major Key/Scale. C Major has no sharps or flats, so in C D E F G A B, C-E is a M3, and C-G is a P5 (remember 4ths and 5th are in the Perfect Family) and that's what you need for a Major Triad. C-B is a M7, and that's what the 7th needs to be for a Major 7th chord.

Now, here's where things get a bit tricky: Does the word "Major" refer to the TRIAD part, the INTERVAL of the 7th part, or BOTH?

The answer is BOTH - but, there are some inconsistencies so bear with me.


Major 7th = Major Triad + M7 Interval, or, Major-Major 7th chord. Some people write this out in some contexts as:

MM7,

because...

The next is called a "Major-Minor 7th chord, or "Mm7".

It is, as you would guess by the name, a Major Triad, with a m7.

MM7 = Major 7th
Mm7 = Dominant 7th.

"wait" "what'd you say"????

That's right, it's called the "Dominant 7th". Why?

Well, it turns out that this particular 7th appears Diatonically on only one scale degree: 5. Or, "V". The 5th note of the scale, as you recall (remember Mediant, Tonic, Submediant - Dominant and all that crap???) is called the Dominant. So this type of structure became called the "Dominant 7th" chord - one that has a Major Triad part and a m7 Interval part.

Some theorists still call it "Major Minor" or Mm7 when they're trying to point out the differences between this and other chords - and help you understand the naming system (becuase Dominant doesn't make sense in the system otherwise) but you'll rarely hear it outside of textbooks.

MM7 = Major 7th
Mm7 = Dominant 7th

Next is the "minor-minor 7th" - a Minor Triad with a m7. That's just called a "minor 7th chord".

MM7 = Major 7th
Mm7 = Dominant 7th
mm7 = Minor 7th

Now the next two "half" and "fully" diminished 7ths. A lot of people are thrown by the "half". Half of what? It makes no sense...

But it does if you understand this "two parts" or "two halves" naming system. You see, in one type of 7th chords, BOTH parts are diminished, so it was "all diminished" or "fully diminished", but in the other type, only HALF of the 2 parts is diminished - the Triad part.

om7 = Half Diminished 7th. That's a Diminished Triad ("o") and a m7 Interval.


MM7 = Major 7th
Mm7 = Dominant 7th
mm7 = Minor 7th
om7 = Half Diminished 7th

In a Fully Diminished 7th, BOTH "halves" are diminished"

oo7 = (OO7 ;-) - it's a Diminished Triad with a Diminished 7th.

MM7 = Major 7th
Mm7 = Dominant 7th
mm7 = Minor 7th
om7 = Half Diminished 7th
oo7 = Fully Diminished 7th

Now, remember how when a chord is a Major chord, we don't say "major" all the time? We might just say "C" and it's understood that without a word behind it it means "C Major".

C
Cm
C+
Co

The "plain" C means C Major.

The same thing happened with 7th chords EXCEPT that it happened not to the Major 7th chord, but to the chord that was actually used far more commonly in music - the Dominant 7th.

So when people say "a 7th chord" or "C7" (usually said "see seven" and not "see seventh" but both are common) that means the DOMINANT 7th!!!

So:

CM7 (or CMaj7, but I'm going to just use "M" for simplicity) = C Major 7
C7 = C Dominant 7
Cm7 = C Minor 7
C%7 = C Half Diminished 7
Co7 = C Fully Diminished 7

the % sign above is used in place of a degree sign "o" with a diagonal "/" through it meaning Half Diminished, which is usually superscript, and the "o" symbol on the Fully Diminished 7th chord, like with the Diminished Triad, should be superscript as well. The numeral 7 is usually also found superscript but it's written so commonly "at baseline" in text and in charts that it's more a matter of taste now.

Additionally, the word "fully" is usually dropped unless the context requires it. So when someone says "diminished 7th chord" they mean "fully" diminished 7th chord.

Finally, it seems so few people actually understand the whole "half" diminished bit that in popular music the name is rarely used. Instead, a more "jazz" oriented name is used: "minor seven flat five" or m7b5 (also m7(b5), etc. That brings up this next bit nicely so:

Let's do them all on C to compare them:

C-E-G-B = MM7, Major 7, CM7

C-E-G-Bb = Mm7, Dominant 7, C7

So, we can of course say a Dom.7 is a Maj.7 with the 7th lowered one Semitone.

C-Eb-G-Bb = mm7, Minor 7, Cm7

You know the Triad part is a minor Triad, so of course its 3rd is lowered as compared to a Major Triad.

But compared to a Maj.7, a min.7 has it's 3rd and 7th lowered one Semitone.

Compared to a Dom.7, its 3rd has been lowered. See all that?

So let's just do the rest:

C-E-G-B = M7
C-E-G-Bb = 7
C-Eb-G-Bb = m7
C-Eb-Gb-Bb = %7 (half dim)
C-Eb-Gb-Bbb = o7 (fully dim - and yes, that's a B double flat!!!)

So you can compare them to each other, reference all of them from Major, or whatever. If you look at a m7, then look at the half dim 7, you can see that the half dim 7 is a m7 with it's 5th lowered, or a "flat 5", hence the name "minor seven flat five" - it's a m7 with b5, or "m7b5".

Now, like Triads, you can also do them by "stacks" of 3rds.

and + Triad is a M3+M3 right?

Well, you can do the same thing here. Of course, hopefully you know your Major, minor, and o Triads stacks, becuase those are the same Triads used here.

So really the only thing new here to learn is the distance between the 5th and the 7th, becuase you should already know the other two!

I'm going to list them in order, so the first interval will be the distance from the Root to the 3rd, the next the 3rd to the 5th, and the last the 5th to the 7th (in bold):

M7 = M3-m3-M3
7 = M3-m3-m3
m7 = m3-M3-m3
%7 = m3-m3-M3
o7 = m3-m3-m3

So another way to do these is look at the Triad part, then the 5th to the 7th instead of the Root to the 7th. And of course, you could look at all the 3rd. For the daring amongst you, you should really look at ALL the interval content - so that includes the two 5ths from the Root to the 5th and the 3rd to the 7th!!!

Some other aspects about how these chords compare may have come to light from the above:

M7 = M3-m3-M3
7 = M3-m3-m3
m7 = m3-M3-m3
%7 = m3-m3-M3
o7 = m3-m3-m3

The only difference between a M7 and 7 is in the distance from 5th to 7th (and of course, Root to 7th, 3rd to 7th, etc.)

The only difference between a 7 and m7 is the Triad part - the distance from the 5th to the 7th (and ergo the Root to the 7th, etc.) is the same.

A Fully Diminished 7th Chord has all m3!!!

There are other observations that can be made, but those are the most commonly noticed or used (aside from those discussed earlier).

Tradition Shmadition, why don't you teach me something useful, like the more modern ones, without getting bogged down in all this "major-minor, "major major", etc. terminology?

OK.

Like we *can* use the Harmonic Minor Scale to build Triads, we can use it to make 7th chords as well.

One Triad, the Augmented Triad, is not found Diatonically (officially) but if we allow the possibility of using Harmonic Minor as a resource for building Triads, we can produce an Augmented Triad (III+ in minor).

Likewise, we can produce 7th chords using Harmonic Minor as well, and that gives us some new and different forms. Let's take C Minor (you remember its Key Sig, correct? Ot at least that you take C Major and lower its 3 6 and 7 to get the Parallel Minor - this is all sinking in isn't it?):

C D Eb F G Ab Bb (C)

To make it Harmonic Minor, we raise the Subtonic (that's Scale Degree 7) to the Leading Tone:

C D Eb F G Ab B (that' B natural) (C)

So only those chords that have the B in them in this case are going to change.

C-Eb-G-Bb originally. Well, what was it before? It's a minor key, so the Tonic chord is Minor. So it's got to be - well heck, there's only one Diatonic 7th chord with a Minor Triad part (!) and that's a m7. Just to be safe, let's check the 7th. C-B comes from C Major, so that would be a M7, and if you decrease the size of a M7 by one Semitone (lowering the upper note, thus moving it closer to the lower note and decreasing the size) you get a m7. So yes, C to Bb is a m7, making this a "mm7".

So what is it now?

C-Eb-G-B

That's a Minor Triad with a Major 7th. Is that one of the traditional 5 combinations? No.

What do we call it?

Guess what, a "minor Major 7th chord".

So, you see, all that traditional naming crap isn't crap after all - they ended up using it here!

CmM7 - a Minor Triad with a Major 7.

Another one with the B in it would be:

Eb-G-B-D

Well, it would have been Eb-G-Bb-D.

What's that?

Gotta go to Eb Major. You may already know that Eb is the Mediant, and thus 3rd scale degree in C Minor, and since we're in a Key, it's Diatonic, and "III" in Minor Keys is a Major Triad, "III", so at least you know the Triad Part is Major. Of our 5 types, that means it has to be either Dominant 7 or Major 7. Guess what - the Dominant is built on the Dominant - is III the Dominant? No, so it's probably a Major 7. Let's check to be sure (and there is an exception to this...)

Eb-D - Well, the Key Sig for Eb Major is 3 flats (just like C minor!) and those are the first 3 in the order of Flats: Bb, Eb, and Ab. Is the D in Eb Major "D" or Db - it's NOT Db because that's not one of the Flats in the Key Sig. So that means D (D Natural) is the "normal" 7th note in Eb Major, so the distance from Eb to D is a Major 7th (because 7ths belong to the m/M family of intervals, and in Major Keys the members of that family (2nds 3rds 6ths and 7ths) are all Major intervals in their "default" state).

Major Triad ("III") + M7 Interval - MM7 - that's a Major 7th, or in this example, EbM7.

Eb-G-Bb-D = EbM7

What's it now though?

Eb-G-B-D = ?

We have a Major Triad whose 5th (Bb) has been raised a Semitone (to B). That makes it an Augmented Triad. Do any of our 5 types have an + Triad for their Triad part? No.

It's a Major 7th with a riased 5th - or "#5". So it uses the same kind of naming that the Half-Diminished got - m7b5 - so we use a chord name it's close to, and add an alteration:

M7#5 - or M7(#5)

The last two chords that contain the B, G-B-D-F and B-D-F-Ab form familiar forms (7 and o7 respectively) so nothing new to learn hear (aside from Diatonic usage, which we'll tackle later).

C-E-G#-B M7#5
C-E-G-B = M7
C-E-G-Bb = 7
C-Eb-G-B = mM7
C-Eb-G-Bb = m7
C-Eb-Gb-Bb = %7 or m7b5
C-Eb-Gb-Bb = o7

Are there more? You betcha!

Two more fall into a category of "altered Dominant 7th chords".

In ye olden dayes, even though they didn't really derive the Augmented Triad from a scale in the way we often think of (often inappropriately) today, they did USE Augmented Triads - mostly on the Dominant - they basically turned the Dominant Triad into an Augmented Triad to give it more "push" to move in the direction it was already going. They also added 7ths freely so inevitably, they came up with another combination we've not yet covered. It became even more common in the late 19th century and into the 20th century (i.e. before Jazz) in music of the Romantic Period.

Simply put, we take a Dominant 7 and make the Triad part Augmented (i.e. raise the 5th) so what we end up with is a "7#5".

On C, that would be C-E-G#-Bb.

Sometimes the term "Augmented 7th Chord" is used because again, when "7th" is used with no other qualifications it's assumed that it's a Dominant 7th".

"Augmented" is taken to mean the Triad part is Augmented (i.e., not the 7th - C-E-G-Bb with an "augmented 7" would become C-E-G-B, simply a Major 7, or if it meant C-E-G-B, then C-E-G-B# would just sound like C-E-G-C!!!!! - so the name wasn't intended that way).

You'll also see C+7, again, the "+" sign meaning the Triad part is Augmented, not the 7th itself.

Finally (for the purposes of our discussion here) the Domininat 7th chord could be altered in another way - lowering the 5th. This makes something totally new and different - in fact, it makes the Triad part a "triad" that doesn't even exist!

Again though, it's just a Dominant 7th chord with a lowered 5th, or 7b5.

C-E-Gb-Bb = C7b5

So, all together:

C-E-G#-B M7#5
C-E-G-B = M7
C-E-G#-Bb = 7#5
C-E-G-Bb = 7
C-E-Gb-Bb = 7b5
C-Eb-G-B = mM7
C-Eb-G-Bb = m7
C-Eb-Gb-Bb = %7 or m7b5
C-Eb-Gb-Bb = o7

Couple of things to think about:

1. Remember that "#" or "b" in the chord's name (aside from the Root letter name it's built on) does NOT mean you're putting a # or b sign on the note necessarily - it simply means it's raised or lowered one semitone respectively (from an assumed default position) using whatever accidental is necessary.

2. Many people prefer the consistency of used the "#5", and "b5" for M7#5, 7#5, and 7b5 because it's already so widely used on "m7b5".

3. Interestingly, those above in #2 took their names from a more "modern" concept, and it even got applied to an older named chord (the half dim becoming m7b5) but the older concept of "MM" and "Mm", etc. got applied to the "mM7". Inconsistent? Yes, but that's tradition and evolution for you.

Now, of course, you could learn the interval formulas for all of these types. Most people just learn the 5 traditional ones and make the alterations from there, in much the same way they might just learn Major and Minor (and maybe diminished, since those make all the diatonic ones) and figure out Augmented from there when working with Triads.

BUt, I'll give you one more way to look at these, and that's the "Major Centric" Reference point. That's where the numbers 1-7 represent the scale degrees of a Major Scale, and everything else is reference from there:

Triads:


1 3 5 = M
1 b3 5 = m
1 3 #5 = +
1 b3 b5 = o

7th Chords:

1 3 5 7 = M7
1 3 5 b7 = 7
1 b3 5 b7 = m7
1 b3 b5 b7 = m7b5 (%7)
1 b3 b5 bb7 = o7

1 3 #5 7 = M7#5
1 3 #5 b7 = 7#5
1 3 b5 b7 = 7b5
1 b3 5 7 = mM7

Learn them all. It's going to take you years. So don't get frustrated. Seriously. Years. The more you use them, the quicker they'll come. But it's not going to be hours or days. Best thing to do is start playing them and figuring them out as much as possible. You might get familiar with Dom 7 and m7 if you play Rock - the other forms are comparatively (comparatively mind you) rare. In Jazz, they're far more common as 7th chord structures are the "basic harmonic unit" in much the same way the Triad is for Classical music and to some degree, rock/pop (though there's always Steely Dan) Take your time, and work on them.

There's more to discuss with 7th chords - and we will - but this will get you started and keep you busy, well, for years.

Links will appear when I recover from writing this post!

Steve


 
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VintagePlayerStrat

Silver Supporting Member
Messages
3,314
That one was a bear. Whew. Yes, years to get down pat.

But now, I think I know what people mean when they say "jazz chords."

They mean 7th chords outside of the Dom 7 and m7 chords used more commonly in Rock -- because Jazz is built around 7th chord structures.

Correct?
 

stevel

Member
Messages
15,132
That one was a bear. Whew. Yes, years to get down pat.

But now, I think I know what people mean when they say "jazz chords."

They mean 7th chords outside of the Dom 7 and m7 chords used more commonly in Rock -- because Jazz is built around 7th chord structures.

Correct?
Yes, as a general rule, we can say that the "base harmonic unit" in Jazz is a 7th chord.

That's opposed to classical music, or other forms of popular/folk music where the Triad is the basic harmonic unit.

In a sense, Jazz made chords "more dense" or "more complex" by "adding notes" to the basic triad form. Most of these are 7ths, but in older Swing for example 6 chords are not uncommon basic forms (like C6) and today a wider variety of non-7th but also-not-typical-triad forms are common like sus chords, quartal chords and add9 chords (all of which could be essentially extensions of 7th chords with the 7th missing!).

So yeah "jazz chords" or jazzy chords would be not A or Am, but A7, Am7, Amaj7, Ao7, A7sus4, A7#5, Am7b5, then all the other 9th, 11th, and 13th chord versions as well as other altered chords and augmented and diminished things...

Or to put it really simply another way - "jazz chords" are "the chords used in jazz" :)

And you're right, while 7ths are fairly common in rock/pop music, and m7s are reasonably common, the rest of those kinds of chords aren't very typical. They do appear, but comparatively speaking, are generally rarer, especially in certain styles. The Beatles use a lot more varied chords and "jazz chords" than do a lot of other bands after - and to be honest they are actually more common than we're led to believe, but they are not the harmonic "foundation" of the style so to speak.

We're seeing a Renaissance of sorts right now with genres like Neo Soul or Neo Jazz etc. which have more of a pop spirit, but include chords like major 7 a lot more now than for a long time (outside of things that were specifically jazz influenced). So we may see a future where more complex chords are used with increasing regularity in pop music.
 






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