>Step by step

Unlocking key signatures

1 Time to meet our old friend the C major scale once again –C, D, E, F, G, A and B. This scale is unique amongst major scales because it’s the only one that has no sharps or flats in it – every note of the C major scale is one of the white notes on the piano keyboard. Because there are no sharps or flats, it doesn’t need a key signature.

2 What makes the scale a major scale is that it obeys a particular pattern of intervals between the notes that defines it as a major scale. This pattern, shown here, is T-T-S-T-T-T-S, where T represents an interval between notes of a whole tone, and S represents an interval of a semitone.

3 Now let’s look at a different major scale – G major this time. You can build a G major scale by applying that same pattern of intervals we’ve just seen, but starting on the note G instead of C. Having done this, we can immediately see one major difference – we’ve ended up with one sharp note in the scale, the seventh F#. degree is an

4 So, here’s a bit of music in the key of G major. If we look at the score, we can see that, as you’d expect with a piece in F# this key, it contains a fair few notes. With all those sharp symbols, it looks untidy and confusing. What if there was a simple way to tell the player that the key of the piece is G major, so therefore every F in the piece has to be played as an F sharp?

5 This is where the key signature comes in! By removing the sharp symbols from the notes themselves and placing just one at the start of the piece, in between the treble clef and the time signature, the player knows that the key is G major and that all of the Fs are to be F# played as s (unless marked otherwise).

6 So this single sharp symbol at the beginning of the tune is the key signature, and its purpose is to indicate to the player the main key the music is in. It’s written so that the inside square of the sharp sign is directly over the note’s position on the stave, and it shows that sharps are to be applied to every instance of the note, in all octaves.