Key signatures, or “key sigs” as the kids say, are how composers write sharps and flats used repetitively throughout a song on the staff. For example, a composer might want to write all F notes in a song as being sharp and so they’d use a key signature.
Key signatures typically appear at the beginning of a piece of music and look like this:
In the above image, you see a F# near the front of the staff. This means that unless otherwise noted all Fs in the song will be played sharp.
So if you see an F like this…
Even though a sharp hasn’t been written beside the F, you will play that F and all others F notes in the song as F# (even if they’re in a different octave).
How Key Signatures Work
Key signatures are very important in music theory because every song is written in a specific key. This requires some explaining so you better follow us into this blue box:
Keys set the sound of a song and control whether it is happy, sad, or something else entirely.
The key signature shows us what key the song is in. You might see zero to seven sharps or zero to seven flats, each illustrating different keys. There are no mixing of sharps and flats.
If a composer wanted to write in a certain key and wasn’t using key signatures they’d have to write a symbol before every note that was to be sharp or flat. This needlessly clutters the music, so songs are written using key signatures to simplify things.
Now that you understand keys, let’s look at key signatures another way.
Here’s a B♭ major scale:
A scale is a series of notes that are arranged in ascending or descending order, as you see above (and by the way, that B♭ major scale is written in the key of B♭).
Using flats we can write the Bs and the E as being flat, as we have done above. We can also use a key signature that says all B and E notes must be flat. That looks like this:
Now when we write the same B♭ major scale like this…
The Bs and the E are played flat as if we had written flats next to each individual note.
That’s the power of the key signature.
Order of Sharps and Flats in the Key Signature
Key signatures are written in a specific order. Here’s what a series of a full seven sharps looks like:
Sharps are always written in the order of F#, C#, G#, D#, A#, E#, and lastly B#.
Music students are taught to remember this order by saying Father Charles Goes Down And Ends Battle – the first letter is the order of the sharps written on a key signature.
A full series of seven flats is always written as follows:
The flats are written in the reverse order of sharps. The order is B♭, E♭, A♭, D♭, G♭, C♭, and F♭.
We remember flats by saying the reverse of “Father Charles goes down and ends battle” – Battle Ends And Down Goes Charles’ Father.
Music is neat!