Grade One Music Theory - Lesson 12: Key Signatures
According to music theory, when we write music which mostly uses notes from the scale of C major and sounds good finished with a C, we say that the music is "in C major".
Here's a short tune in C major:
If a tune mostly uses the notes from the G major scale and sounds good finished with a G, then the music is "in G major". Here's the same tune as above, but now it's in G major:
As you know, in G major the Fs are sharp. Instead of writing all the Fs in the piece with sharp signs next to them, we write just one F sharp, right at the beginning of the line, after the clef and before the time signature. This is called the "key signature". (We don't use a key signature for music which is in C major, because we don't need one! - C major doesn't have any sharps or flats!)
In the treble clef, we always write the F sharp sign on the top line (we never use the lower F space). You should be able to just see the line of the stave between the two horizontal lines of the sharp sign.
In the bass clef, we write the sign for F sharp on the second line from the top.
The key signature is written at the beginning of every line of music, immediately after the clef, to remind us that all the Fs need to be F sharps.
Let's look at D major next:
D major has two sharps - F sharp and C sharp.
The key signature of D major in the treble clef looks like this:
We add the C sharp to the F sharp that we've got already.
In the bass clef, the key signature of D major looks like this.
Finally, let's look at the key signature for F major. Remember that in F major there aren't any sharps, but there is one flat - B flat.
In the treble clef, the flat is written on the middle line.
In the bass clef, the flat is written on the second line from the bottom.
For Grade One Music Theory, you only need to know about these three key signatures: G major, D major and F major (and you need to know that C major doesn't need one!)