Building other keys in the diatonic scale

Click here for the general overview

In the previous blog, we saw how we could find the notes on the guitar neck using the diatonic scale in the key of C.

We also found out about sharp and flat notes : a note that is raised half a step is called “sharp” (e.g. F#), and a note that is lowered half a step is called “flat” (e.g. Bb). We did also see that a sharp and a flat note can sound the same, e.g. C# and Db, but I re-assure you that they are not the same. The current blog, and the next one, will explain why.

But now, it’s about time we set out to build other keys in the diatonic scale. And you can do this in 2 ways : "the wrong way, or my way" as Oliver Hardy would have put it.

The "wrong" way would be to apply the diatonic scale to a random note, say B. It's not "wrong", in that if you apply the pattern, you will eventually get the scale. But it's a cumbersome, not well thought out manner.

There is another method - I won't reveal the name of it yet - that yields results much faster and efficient. So, let's take that route !

Have a look again at the pattern in the key of C :

or in a more schematic way :

If you look closely, there's a sub pattern hidden there. That sub pattern is :

or “1 step – 1 step – 1/2 step”.

It's also known as a tetrachord. There are 2 tetrachords in the diatonic scale, connected by a whole note, like this :

It seems that the diatonic scale is built on 2 mini-scales !

Now, if I were to ask you to build the diatonic scale in another key, in other words, starting on another note, what note would you choose ? D ? E ? Any other ?

Well, I would choose G.

Why ? Because I’m lazy !

Let me explain : the diatonic scale has 2 “mini-scales”, 2 tetrachords. If I start the diatonic scale on G, I already have 1 “mini-scale” for free : it’s already there ! There’s no other note in the key of C that offers that advantage !

Ok, so let’s start with G, and write down the notes we know in the key of C :

 

 

There you have it. “Houston, we have a problem.”

 

If we play the notes of the key of C starting on G, we don’t get the pattern of the diatonic scale !

 

Let’s analyze this more closely. The first “mini-scale” seems ok, I mean, that’s why we started on G in the first place. Also, the connecting interval (between the 4th and the 5th note) is a whole tone, as required.

 

The trouble is in the 2nd tetrachord. In stead of the pattern “1 step – 1 step – 1/2 step” we get : “1 step – 1/2 step – 1 step”.

 

Let’s lay this problem out on the guitar. Luckily, we have a G-string (3rd string) we can use to play the scale from the open string to the 12th fret :

 

 

Now, that you see it on the guitar, isn’t the solution obvious ? What do we have to do in order to make the F half a step closer to the octave G ?

 

Right ! You have to raise it half a step ! So, in stead of playing F, you play F#, like so :

 

 

Schematically, this is the result :

 

So, if you play an F# in the key of G in stead of F, everything is ok !

We could put it even more strongly, and state that there's only 1 key in the diatonic scale that has 1 sharp note, and that's the key of G !

In other words :
If you have 0 sharp notes, you are in the key of C.
If you have 1 sharp note – which always will be F# – then you are in the key of G.

Okay, let’s move on !

Now, building on the key of G, if I were to ask you to play another key, in other words, choosing another note to start playing the diatonic scale, what note would that be ?

Well, I would choose D. And for the same reason : the first mini-scale I need already there ! Starting the diatonic scale on D, I have 1 “mini-scale” for free !

If you write down the notes of the key of G, starting on D, then you get this :

 

Again, we run into trouble : the pattern is broken !

After a quick analysis we find that it’s the same problem as with the key of G : it’s the 7th note, in this case C, that causes the problem.

Let’s see this on the guitar. I’ll use the 4th (D) string to play the scale from open string to the 12th fret :

Notice that I play F# and not F, because our base was the key of G, not C !

Also, notice that the solution is again very obvious ! Don’t you see it ? Of course you do : if you raise C to C#, you regain the diatonic pattern :

Or schematically :

 

So, the key of D requires 2 sharp notes : F# (coming from the G-key) and now the C#.

 

Let's recap what we have :

no sharp notes : key of C

1 sharp note F# : key of G

2 sharp notes F# + C# : key of D

 

Now, let me ask you these questions : what key would you build next ?

And on what note do you expect a problem ?

And how do you think you can solve that problem ?

And last question : how many sharp notes would you have in that key ?

 

Think about this for a while before you read the answers below….

 

Well the answers are :

 

the key I would build next is the key of A, because the first mini-scale would already be there.

 

I expect to have trouble at the 7th note, which in this case would be G.

 

I would solve that problem by raising the G half a step to G#.

 

So, the key of A has 3 sharp notes : F# (coming from the key of G), C# (coming from the key of D) and now my own G#.

 

So, again let’s recap :

 

0 sharp notes : key of C

1 sharp note F# : key of G

2 sharp notes F# + C# : key of D

3 sharp notes F# + C# + G# : key of A

 

Using this method, you can continue to build other keys. And I suggest you do that one more time. (What key would you have ?)

 

If you continue after that, you’ll end up eventually raising all the notes, even the B to a B# ! And, eventually, you would come full circle : from the key of C, you would end up in the key of C.

 

Here’s another thing to notice : every time we started a new key, we used the 5th note :

from C we took the 5th note G to build the key of G

from G we took the 5th note D to build the key of D

from D we took the 5th note A to build the key of A

etc..

 

So, there is a very appropriate name for this method we used to build keys. It’s called :

 

“The Circle Of Fifths” !

 

How great is that ? Now you know what is meant by “The Circle Of Fifths” ! It’s the method of building keys on the 5th note of the scale, adding more and more sharp notes as you go.

These sharp notes will always be in this order : F# + C# + G# + D# + ….

Also notice that the distance between those sharp notes are also 5 notes, e.g. between F# and C# (F# – G – A – B – C#).

 

If you’re main interest is to play folk or bluegrass music, then the keys that we’ve built in this Pomodoro are all you need : the keys of C, G, A, D and sometimes E cover almost all of the folk and bluegrass songs !

 

But if you are into jazz, you’ll have to learn to build more keys. And that’s what we’ll do in the next Pomodoro.