I have trudged through the jungle of online music lessons encountering bloggers, YouTubers, and influencers galore struggling to explain how to name the notes in any given key. 

 “If you are descending”, they say, “it’s Ab. If you are ascending, it’s A#.” Bach would roll in his grave to hear such absurdity. 

In this article, you will learn how to name the notes in any key signature once and for all. So let’s get started. 

Law number one

Every key has seven notes

There are 12 notes in western music theory including accidentals. Each accidental has two possible names. 

1) A
2) A sharp or B flat
3) B
4) C
5) C sharp or D flat
6) D
7) D sharp or E flat
8) E
9) F
10) F sharp or G flat
11) G
12) G sharp or A flat 

In some atypical keys, you will find a few curious occurrences. In the key of G flat, for example, you must call the B note "C flat", but more on that a bit later. There are also theoretical keys such as F flat major which contains a double flat. B double flat in that case. But now is not the time to go off the rails here. You will never experience these keys playing modern western music unless you advance to progressive rock or some avant-garde forms of neo-prog complex virtuoso fusion. But I digress. 

So let’s get back to law number one. 

Every key has seven notes

In music notation, a flat is designated by the “b” sign, and the “#” sign designates a sharp, so let’s use that notation from here on out, shall we? 

You probably know by now (if you have any music knowledge whatsoever) that the key of C has no accidentals. Neither does its relative key of A minor, but let’s not consider minor keys for now because they have the same notes as their parent key, just starting in a different place in the scale. Don’t let me confuse you. Let’s not think about minor keys at this point. 

Law number two

Every major key (major scale) has the following formula: Whole step, whole step, half step, whole step, whole step, whole step, half step

The distance (or interval) between each of the twelve notes is one half step. Two half steps make up one whole step. There’s not much complex math here, so stick with me. If you play every white note on the piano starting on C and ending on C, you will notice that you are playing a major scale. Every time you play two white notes in succession without a black note between them, you are playing the interval of a half step. Every time you play two white notes in succession that do have a black note between them, you are playing the interval of a whole step. So playing all the white notes from C to C is following law number two. See for yourself as you examine the white notes while playing them, and listening for the major scale sound, i.e. the do-re-mi sound. 

So now we are ready for the good stuff. Let’s see what happens when we start on A and follow the ‘law number two’ formula. In other words, we will play a major scale starting on A. So first, play A. That will be the root note in the key of A. One whole step up from A is B. So far, so good, right? No black keys yet. One whole step up from B is C#. Our first black key. To follow the ‘law number two’ formula, we must play C# because there is no black key between B and C. That means from B to C is only one half step. So to play a whole step from B, we must go to C#. But wait! We could also call C# Db. So here comes law number three. 

Law number three

Each of the seven notes must be present and present only once

If we use A, the next note must be some kind of B. The next note must be some kind of C, etc. So we can’t go from B to Db in our A major scale because we would be skipping C. So continuing our A major scale: A, B, C#, D, E, F#, G# A. We have seven notes, and each letter name is used only once, and we are following our ‘law number two’ formula. 

What if we play a G major scale? G, A, B, C, D, E, F#, G. We must use the letter name F# and not Gb because we would be skipping a note with the F name, violating rule three. How about an F major scale? F, G, A, Bb, C, D, E, F. In this case, we must use Bb and not A# because we would be using the A name twice, violating rule three. 

All the major scales are written in stone. I.e. Eb major will always be Eb, F, G, Ab, Bb, C, D, Eb. Memorize it. Take it to the bank. It will never change. And as you memorize the major scales, you will notice specific patterns emerging that will help you to learn them all. For example, compare the Eb major scale above, to E major: E, F#, G#, A, B, C#, D#, E. Every flat note becomes natural, and every natural note becomes sharp. If you say each scale out loud, you will notice that they have the same sing-songy cadence. This will help you to memorize them. In this way, learning all the keys with sharps will automatically teach you all the keys with flats.  

So there you have it.  

1) Every key has seven notes. 

2) Every major key (major scale) has the following formula:
Whole step, whole step, half step, whole step, whole step, whole step, half step. 

3) Each of the seven notes must be present. And present only once. 

With this knowledge under your belt, you are on your way to learning all your key signatures, advancing one step closer to becoming a music theory ninja.