On occasion, you may, as a guitarist, run into a situation where you will run into double sharps and flats. The good news is that it is rare in popular music. The bad news is that you still may run across them now and then, and you may as well learn how to cope with them.

Let's start this off by talking about keys and major scales in particular.

Recall that major scales have a formula ( 1 + 1 + 1/2 + 1 + 1 + 1 + 1/2)

There are also rules concerning the construction of these things:

1. You must use every letter of the musical alphabet ( ABCDEFG ). You cannot skip a letter. Ever.

2. You must use the major scale formula.

3. You must never mix sharps and flats in the same scale. A major scale will have sharps in it, or flats in it, or none of either.

So, if I wanted to construct an A major scale, I would start off with rule number 1 -- Use every letter.

A B C D E F G.

Now it becomes a matter of whether or not there are any sharps or flats. So let's apply the formula:

1 step above A is B

1 step above B is C#

1/2 step above C# is D

1 step above D is E

1 step above E is F#

1 step above F# is G#

1/2 step above G# is A

So my A major scale is: A B C# D E F# G# A (There are 3 sharps in this key C#, F# and G#)

Most of your "pop keys" will not have more than 5 sharps, but what if I'm in the key of G#? Let's construct this headache of a scale:

1. Use every letter. I will start by using G# because I know that that is the key. I also know that I will be using sharps and not flats because I cannot violate the rule that concerns mixing sharps and flats. But at this point I don't know where these are so:

Rule number 1 -- Use every letter. G# A B C D E F G#

Rule number 2 -- Apply formula ( 1 1 1/2 1 1 1 1/2 )

1 step above G# is A#

1 step above A# is B#

1/2 step above B# is C##

1 step above C## is D##

1 step above D## is E##

1 step above E## is F##

1/2 step above F## is G#

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

Look at all of the pretty double sharps! What's up with that and how did they get there?

In truth, these guys are a pain for any musician. It forces even the best and most cultured musicians to "think fast" (as you can imagine). But they are not hard to understand if you know what a sharp (#) really does.

A sharp (#) raises a note 1/2 step. That is the definition of a sharp. So, for example a C## is a C raised a half step twice.

Now let's look at the Chromatic Scale:

A A#/Bb B C C#/Db D D#/Eb E F F#/Gb G G#/Ab A

Recall that this baby is a 1/2 step scale. That is, the numeric distance between each and every note in this scale is 1/2 step.

Now, what does a sharp do? It raises a note 1/2 step.

That means that if I wanted to (I wouldn't, by the way) I COULD express a D as A##### (D raised a 1/2 step 5 times)

1/2 step up from A is A# (raise number 1)

1/2 step up from A# is B (raise number 2)

1/2 step up from B is C (raise number 3)

1/2 step up from C is C# (raise number 4)

1/2 step up from C# is D (raise number 5)

Fortunately you will never, ever see this to this extent -- it's too demented even for classical music.

But you will see double sharps on occasion.

So going back to the despised G# major scale

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

A B# is really a C, but because of the rules of major scales it has to be represented as a B#.

A C## is really a D, but because of that rule, it has to be represented as a C##.

A D## is really an E.

An E## is really an F# (This one's fun!)

An F## is really a G

So, if you have the misfortune of seeing a piece of music in the key of G#, you might run across an E##m7 chord -- which is really F#m7!

Now ain't that special?

Again, you may play for years before you are forced to deal with something like this on a practical level (and certainly not to this extent. A piece of music will be written in Ab rather than G#). But sooner or later you will, so it's important that you understand what's going on.

Now dealing with double flats is the same problem -- only in reverse. The definition of a flat is to lower a note 1/2 step.Double flats are far less common though.If you can understand double sharps, you won't have much of a problem understanding double flats.