Chords

A chord is when 3 notes or more are played at the same time. The 1st note of the chord is the root note and the distance between the notes gives the chord its overall sound. You probably already know that there are several different types of chords, such as: Major, minor, dominant and suspended chords. Each has it's own unique sound and there are many more types than are listed there.
In this reference guide we'll look at where chords come from, how they differ from each other and how the notes within the chord change it's sound.

Chords from Scales

The notes that create the chords for a key come from the scale of that key. Each note in the scale can be considered the starting point or root note for one of the chords. If we were using the key of C Major the root notes of the chords would be:

To find the next note of each of the chords we would then count along 3 notes from the root note including the root note as one so:

C	D	E	F	G	A	B
1	2	3

we now have C and E.

If we repeat this step from the E in our chord:

C	D	E	F	G	A	B
		1	2	3

we get a G so our notes for the chord are now C, E and G. Since we only need 3 notes to make our chord we can stop here.

This process can be repeated for each of the notes in our scale and we would end up with:

G	A	B	C	D	E	F
E	F	G	A	B	C	D
C	D	E	F	G	A	B

Our first step of turning a scale into chords is done. The next step will be to figure out which chords we have.

Chord Construction

At this point we need to look at chords that we know already and work out a numeric formula for each different type. To do this just follow these steps:

Play a known chord e.g. C Major
Write down all of the notes in the chord, starting from the root note – C E G C E
If you have more than one of the same note in the chord you can ignore the extra ones – C E G ~~C E~~
Next, make sure the notes are in alphabetical order starting from the root note.
In our case ( C E G ) the notes are already in alphabetical order but some guitar chord shapes have the notes in a different order which would affect the subsequent steps of this process.
Find out where each of these notes lies in the appropriate scale:

1 3 5

C E G

This gives us a numeric formula for working out which notes of the scale make up a Major chord – the 1st note, the 3rd and the 5th.
If you apply this formula to any key it will always work out the appropriate notes for a Major chord. Test this out with a different key then compare it to a known Major chord in that key. First work out the 1st 3rd and 5th notes of the scale in, say, G then check these notes against all of the notes in an open G Major chord.

Different chords

If we follow the same system as above to work out a minor chord's formula we can then compare it with the Major chord’s formula and see the difference between the two.

Play a known minor chord (this doesn’t have to be the same key as the chord above) – A minor
Write down the notes of the chord starting from the root note – A E A C E
Remove the doubled notes – A E A C E
Place the notes in alphabetical order from the root note – A C E
At this point it is worth pointing out that it is usually easiest to still use the Major scale even though our chord isn’t a Major chord; the reason for this is that as we work out the notes of our chord we may find that the note we’re looking for isn’t in the Major scale and so we have to alter the scale note to make our chord note fit. It’s as we alter the scale note that we see how to alter the formula's number (this will make sense in a minute when we do the next steps)
Find the position of the notes in the same key -

A C E

1 b3 5

We found that the A Major scale has C# not C as its 3rd note so what we had to do was flatten the 3rd note to get C hence b3.
Now that we have two different chord's formulae we can compare them –

Major
1	3	5
minor
1	b3	5

We can now see that the only difference between a Major chord and a minor chord is the 3 – if it’s flat the chord is minor if it’s natural the chord is Major.

The system from above can be applied to all chords to work out their formulae. Luckily for you I’ve already compiled a list of the most popular chords:

Chord Formulae Dictionary

Chord Name	example	Chord Formulae
Major	A \| A Maj	1	3	5
Major 7th	AM7 \| A Maj7	1	3	5	7
Major 9th	AM9 \| A Maj9	1	3	5	7	9
minor	Am	1	b3	5
minor 7th	Am7	1	b3	5	b7
minor 9th	Am9	1	b3	5	b7	9
Dominant 7th	A7	1	3	5	b7
Dominant 9th	A9	1	3	5	b7	9
Dominant 11th	A11	1	3	5	b7	9	11
Dominant 13th	A13	1	3	5	b7	9	13
Suspended 4th	Asus4	1	4	5
Suspended 2nd	Asus2	1	2	5
7th Suspended 4th	A7sus4	1	4	5	b7
Diminished 7th	A° \| Adim7	1	b3	b5	bb7
Half Diminished 7th	A^1/2dim7 \| Am7b5	1	b3	b5	b7
6th	A 6	1	3	5	6
Minor 6th	Am6	1	b3	5	6
Added chords	Aadd9	1	3	5	9
Added chords	Amadd11	1	b3	5	11

Revisiting Chords From Scales

Now that we have our formulae above we can look again at the chords we found when we used the Major scale to create our chords.

G	A	B	C	D	E	F
E	F	G	A	B	C	D
C	D	E	F	G	A	B

If we take the time to work out what each chord is we would have a chord system for the Major scale in general; this would be very useful as it would tell us which chords are available for any key.
We already know CEG is a Major chord (and this makes sense since it's taken from the C Major Scale).

To find out the rest of the chords we just follow the same system from the Chord Construction section above. Remember to always figure out the formula for the chord in it's own key i.e. DFA should be found from the Major scale in D; EGB should be found from the Major scale in E etc.

Once we have done this for each chord we would have all of the formulae for the chords in our key. Comparing the formulae to our list above we find that:

C is a Major chord
D is a minor chord
E is a minor chord
F is a Major chord
G is a Major chord
A is a minor chord
B is a diminished triad

We can now use this sequence of chords for all Major keys:

I	II	III	IV	V	VI	VII
Major	minor	minor	Major	Major	minor	diminished

Roman Numerals?

As an example of this chord system in use we could take another key; let's use G Major:

G	A	B	C	D	E	F#
Major	minor	minor	Major	Major	minor	diminished
I	II	III	IV	V	VI	VII

You could go through the chords from scales process above to check that the system works, or you could take my word for it, it's up to you.
What does this really mean? How does it help you? Well now if you were ever wondering what chords would sound good together to make your own song or how songwriters know which chords work together, there's how. Try playing them in different combinations to see what works.

Extending Chords

At the beginning I mentioned that you can extend chords by following the same system as above. Let's do that now to see what happens:

B	C	D	E	F	G	A
G	A	B	C	D	E	F
E	F	G	A	B	C	D
C	D	E	F	G	A	B

Now using the appropriate scale for each chord we find out where each note lies:

The C chord has the notes: 1 3 5 7 - so look in the dictionary and we see that means our chord is a CMajor7
The D chord has 1 b3 5 b7 - this means the chord is a Dminor7
The E chord has 1 b3 5 b7 - so it's E minor 7
The F chord is 1 3 5 7 - so FMajor7
The G chord is 1 3 5 b7 - this is different
All of the other Major chords turn into Major 7s but this one (the 5th chord) becomes a dominant chord. Although the dominant chords are based on a Major triad (1 3 5) they have a b7 note. This chord plays an important role in chord progressions.
and is a dominant 7.
The A chord has the 1 b3 5 b7 notes and so is another minor 7th
The B chord has 1 b3 b5 b7 notes so this is a half diminished chord, looking at our list another name for it is minor 7 flat 5!

So with the chords extended our chord system for the key would look like this:

I	II	III	IV	V	VI	VII
Maj7	min7	min7	Maj7	Dominant 7	min7	^1/2dim7

Something to bear in mind is that all of these chords are included in the same key so in G you'd have G Major and GMaj7, E minor and E min7 and so on.