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  • Writer's pictureTom Glasson

7ths

Welcome to this Music Theory Centre tutorial. This lesson is about 7ths - the different types of 7th chords, how they are built and where they might be used. If you've ever been confused about 7ths, that is about to change.


Video Tutorial:




7th Graphics
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TRIADS

We will start this lesson with the basics of Chord construction. This will be covered in more detail in another lesson, but here is a quick guide, as it will be important to understand 7ths.


Chords are built from something called a triad. This is the first, third and 5th. 


Tonic Triad
Tonic Triad

These numbers come from intervals. Start with the note you want the chord to be, for example for a D chord, the first is a D. Then we count up, the third will be an 'F' of some kind, and the 5 is an 'A' (which is the 5th letter of the 'D' scale).


There are two main type of triad, a major triad and minor triad. And there are some others which will be in different lessons, for now we will focus on these main two triads.


Both of these triads start with the root, numbered 1. And both use the same 5th - this is called a perfect 5th, as it is the same for both major and minor triads. If you don't quite understand that, check out our lesson on intervals for more on this topic.


The difference between the major and minor triad is the third. This will be a minor third for minor triad or a major third for a major triad.

Major & Minor Tonic Triads

Minor thirds are 3 semitones (above the root/1st) while major thirds are 4 semitones from the root. 


So in D:

D Major - D, F#, A (F# is 4 semitones above D)

D Minor - D, F, A (F is 3 semitones above D)


Extensions

Extensions are essentially additions to this triad. You can add all sorts of other notes, usually named by the interval number. So simply, 7th chords are adding the interval of a 7th to the triad - 1st, 3rd, 5th, 7th.


Extensions are usually spelt over two octaves, so you could have a 9 chord, 11, 13 or 6 as example, and they all add the described interval to the chord, look at these examples.


Chords with Extensions
Triads with Extensions


This lesson is about the extended chord called the 7th.



7ths

The most common extension is called the 7th. 


Continuing the example in D, the 7 for a D triad will be some kind of a C. It’s always the note before the octave. For example;

  • the 7th of a G is F,

  • the 7th of a B is an A


D triad with 7th
D Triad with 7th

The same way the third can be minor or major, so can the 7.


The minor 7 is a 10 semitone interval

The major 7 is an 11 semitone interval

 

This means there are 4 combinations of 7th chord that we can make. Remember, these are built on the minor or major triad.


The Minor Triad can have a major or minor 7th added and

The Major Triad can have a major or minor 7th added.



7th chords chart

These all have different names based on the type of 7th it is. These are:

  • Major 7

  • Dominant 7

  • Minor 7

  • Minor major 7


The 4 types of 7th Chord
The 4 types of 7th Chord


Let’s look in detail:


MINOR 7

Firstly is the most simple, the minor 7 adds the interval of a minor 7 to a minor triad. This is the 7th degree of the minor scale, so Am7 will add a G, which is the minor 7th interval or as we saw - 10 semitones (A to G)


A Minor 7
A Minor 7

We are adding the 7th interval to the chord on top of the root, minor third and 5th.


So C minor 7 is: C, Eb, G and then Bb.



C Minor 7
C Minor 7

Another way to look at it is that the minor 7 adds the 7 which is one tone down from the octave or root. This is just a faster way to find the note.


DOMINANT 7

The next type of 7 is called the Dominant 7.


This one is the same as the minor 7 except it is built on a major chord. So the first, major third, fifth then minor 7. For example G dominant 7 is G, B - major third is 4 semitones, D, and F - 10 semitones (G to F)


G Dominant 7
G Dominant 7

But, if chord was in the key of 'G', the 'F' should be an 'F#' in this key, not 'F'...


This is what the Major 7 does.


MAJOR 7

The major 7 is the same as dominant 7 except in uses a major 7 interval instead of minor 7. Remember minor 7 is 10 semitones, major 7 is 11.


Here is the G again, but this time it has a Major 7.


G Major 7
G Major 7

The Major 7 is essentially a semi tone down from the octave (or root) rather than a whole tone - If you wanted to find it quickly.


USING 7th CHORDS

So, how are these chords used in a key?


Well really, you can play them however you want, if it sounds good, it is good!


But the typical rule is:

The minor chords in a key use minor 7,

Then the 5th, uses the dominant 7, and

The first and 4th use major 7.


the 7ths in a key
The 7th Used for Each Chord in a Key

Here they are in the key of C major,


  1. C Major 7

  2. D minor 7

  3. E minor 7

  4. F Major 7

  5. G Dominant 7

  6. A minor 7


This chart is available to download at the top of this page.


This arrangement of 7's use the notes which are within these key signatures, but there isn't a reason you can't use a 7th from outside the key. That's down to your taste. You can use a dominant 7 for chord 4 or major 7 for chord 5. Things like this are often used to help change key or move to different parts of a piece of music.


You may have noticed there is one 7 we haven't covered yet.


MINOR MAJOR 7

The last one on the list is the minor major 7. Which is exactly what it sounds like its the minor triad with a major 7.


In C, this is C, Eb, G but with the major 7, B Natural.


C Minor/Major 7
C Minor/Major 7

It sounds suspenseful and mysterious… have fun with it.




A Free Gift for you...

Download the Grade 1 Music Theory Workbook - An Introduction to Music Theory for free. The workbook is a written course which teaches you the entire content of Grade 1 music theory from start to finish, it is the full written version of our video course. It contains activities, with answers, to test your knowledge and give you chance to practice what you are learning.


There are 19 sections, covering every topic as well as reference sheets and materials which will come in handy as you study.


Click here to check it out.


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