How Do Key Signatures Work?

In the last couple days I’ve received two requests to explain key signatures. Both people had different applications for their question, so the answer to each was different. Here I’ll explain key signatures and the most common uses for that information.

I’m going to start with a quick cheat sheet on how to figure out key signatures. Then further below you can read the technical reasons behind what we’re doing here (if you can stay awake through it).

NO key signature is key of C major. One flat (Bb) is the key of F major.

Key Signatures – SHARPS
Order of Sharps is: F-C-G-D-A-E-B
Remember this by “Fat Cats Go Down And Eat Breakfast”
To Figure Major Key: Go up 1/2 step from the last sharp and that is your key.
Example: Key signature shows 3 sharps, they will HAVE to be F-C-G. That last sharp is G#, go up 1/2 step from G# and you have A. So three sharps is the key of A Major. This means if you play from A to A with the sharps of F, C and G – you will have a major scale. (Note: songs can also be in minor keys and other modes, explanations on that below).

Key Signatures – FLATS
Order of Flats is: B-E-A-D-G-C-F
Remember this by “BEAD – Greatest Common Factor”
To Figure Major Key: Next to the last flat is the name of key.
Example: Key signature shows 3 flast, they will HAVE to be Bb-Eb-Ab. The NEXT TO THE LAST flat is Eb (or count three flats B-E-A, then count back one to Eb) – Your key is Eb Major.
Note: Because one flat is Bb and there is no where to count back, you should memorize that one flat – Bb – is the key of F major. (Ok, let’s get technical, when you count down from the last flat, you are actually coming down a perfect fourth – and a perfect fourth down from Bb is F – so that’s really what’s happening).

You Don’t Know It Until You Need to Know It
I’ve had piano students sit in a fog when they first learn key signatures. They are in a fog until we use the information as a real application. A good way to force you to know key signatures is to transpose. Take a song and transpose it up a whole step. In order to do this, you’ll need to know what key you are in and what key you are going to. I make students do the whole process in their head so they know EXACTLY what they are going to do before they start playing. Doing it by ear does you no good for understanding the theory behind it.

What is a Major Scale?
If you play from C to C on a piano, that is a C Major Scale. What makes it a C Major Scale is the combination of whole steps and half steps. You’ll notice a half step between E-F and B-C – the other notes have a single black note between them which is 2 half steps – and 2 half steps is called a “whole step”.

A “tetrachord” is the four step series of: whole – whole – half (on a piano this could be C-D-E-F – the first C-D being the first whole step). A major scale is comprised of two “tetrachords” back to back – the second tetrachord starting a whole step from the first one. In a C Major Scale the two tetrachords are C-D-E-F and G-A-B-C.

What Is a Key Signature?
A key signature is the listing of sharps and flats at the beginning of a music piece. These sharps and flats are to be played through the entire piece or until the key signature changes. If there are no sharps or flats at the beginning of the song, then you are usually in the key of C Major (or A minor, more on that later) – or the composer chose to write in his accidentals manually and doesn’t like using key signatures (this is more common in contemporary music, and the bane of most studied pianists).

Why Do We Need Key Signatures?
All that information is fine for the key of C – but if you want to play a major scale that starts on a different note you’ll need to start using sharps and flats (usually black notes on a piano) to create that same series of whole and half steps. For example: Play from F-F on all white keys. Notice how it sounds just a little odd, not quite like a major scale? That’s because the fourth step needs to be a half step, which would be Bb. So it is that in the key of F major, the key signature is Bb.

Why Do We Need to Play in Different Keys?
This is actually a common question, why can’t we just play everything in C Major? Aside from that idea being boorish – first think of male and female singers. They have very different ranges – so a melody that works well for a soprano might need to change to be sung by a male bass. Or instruments, an oboe concerto may need a different key than melodies played by trombone, etc. Artistically, many people claim that certain keys have certain “moods” – and many composers also believe this. For me, I think there are certain keys in different eras that are used more than others, and knowing that can help dictate your key if presented with multiple options.

What Is a Minor Key?
The minor scale is the scale that starts on the 6th step of the major. These keys are called “relative keys” because they share the same key signature. If you are in C Major – then the relative minor key is A minor (A is the sixth step of the key of C). Playing A to A on a piano using just white notes will give you an A Natural Minor Scale. For an A Harmonic Minor Scale, just raise the 7th step (G#). For an A Melodic Minor Scale raise the 6th and 7th steps going up (F#, G#) and leave them nature when coming down (F, G).

If you are confused about minor scales and what I just said, don’t worry about it. The only thing to understand is that a key signature does not always mean the major key, it can also designate the relative minor. MOST music (99%) is either in the Major or the Minor (Aeolian – minor key 6th step) key. Once you’ve made the mistake several times of thinking it was the major, you’ll remember it.

QUICK KEY SIGNATURE CHEAT TIP: Most songs begin and end on the root chord of the key. If your song starts on an A chord, there’s a good chance the song is in A Major. (Second most popular intros are on the 4 or 5 chord). So a quick scan of the first and last chord of the song may help you in determining if you are in a major or a minor key.

How Long Does It Take a Seasoned Musician to Identify a Key Signature?
Assuming they are used to reading scores – under three seconds. That’s including 1.5 seconds for a page turn.

Circle of fifths is a fun thing that will really blow open your sight reading and improvisation once you understand it. My concert master actually has the circle of fifths tatooed on his arm! That’s how much fun it is. But until you get it, it’s a confusing messy thing. There are many approaches to this, but I’ll just give you what I think is most important:

Circle of Fifths could also be called Circle of Fourths, because a Perfect 5th up is the same as a Perfect 4th down, and vice-versa. If you follow the key signatures as you add sharps or flats, you’ll notice a sequence that the keys are moving by perfect fifths – C – G – D – A – E – B – F# (Gb) – C# (Db) – G# (Ab) – D# (Eb) – Bb – F – C. Do you see it now?

But that’s not the fun part, the fun part is seeing how this movement can work with chords as well, let’s start at B and work backwards to C. Play chords F#m – B – E7 – Am – D7 – G9 – C. Now you have a nice little jazz progression. Start noticing how many times little circle of fifth patterns are used in music. 5 to 1 is the strongest movement in music, and the 5 of 5 is the major two, the 5 of 2 is the major 6 and so on.

Want to REALLY see the circle of fifths in action? Start sightreading through jazz standards from the 30’s and 40’s – you’ll see circle of fifths patterns all over the place. A good way to work on 9th chords to. Did jazz invent the circle of fifths. No. My FAVORITE example of circle of fifths patterns is a long descending bass section in JS Bach’s Brandenburg Concerto #3. I rip that off all the time when I’m doing classical improvisations. Classical and Baroque music uses it quite often as an “escape” to move to a new section or to return to a statement of the main theme.

If you use all this information as you study, eventually it will become second nature. If you don’t have to use it, it will forever remain a fog. If you are a lifetime player or pro musician (more specifically if you are a music arrange or music producer), then I really think you MUST digest and internalize all of this. If you are a weekend warrior or play by ear, don’t worry about it. Just memorize the key signatures.

I certainly am glad I don’t have to go through the pain of learning all this again. šŸ™‚


  • I was actually looking for a website at which I could download a hymn in a certain key, when I stumbled across your website. What a delight! I’ve, for whatever reason, remembered that the next to the last flat is the key, but I had forgotten that 1/2 step up from the last sharp is the key. (Or perhaps I was asleep when that was presented!) Anyway, I enjoyed your website.

    Now it’s back to my search.


  • Ever since I first started to learn my key signatures, I’ve found the easiest way to remember the order of sharps and flats is:

    For Sharps: Father Charles Goes Down And Ends Battle.

    This is really awesome because if you say it backwards, it’s the order for flats and it still makes complete sense:

    With Flats: Battle Ends And Down Goes Charles’ Father

    !! Its what I’ve used for 8 years of theory … hope this helps

  • Thanks. I am learning to read music and this helps a lot. See, my problem is that I have allready wrritten some songs for my band, but now Im going back to figure out the keys of these songs, and they don’t seem to fit in any key. It’s so confusing.
    My question is that (for example) if you have a song in the key of G, is it ok to add in a B flat? If so, is it still in the key, or does that mess everything up?
    Please help me figure this out,
    Thanks, Brendan

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