Key signatures
The sharps or flats right after the clef tell you which notes to change for the whole piece. There are fifteen, and two rules name any of them in a second.
Every key signature
| Major key | Relative minor | Signs | Which |
|---|---|---|---|
| C♭ major | A♭ minor | 7♭ | B♭ E♭ A♭ D♭ G♭ C♭ F♭ |
| G♭ major | E♭ minor | 6♭ | B♭ E♭ A♭ D♭ G♭ C♭ |
| D♭ major | B♭ minor | 5♭ | B♭ E♭ A♭ D♭ G♭ |
| A♭ major | F minor | 4♭ | B♭ E♭ A♭ D♭ |
| E♭ major | C minor | 3♭ | B♭ E♭ A♭ |
| B♭ major | G minor | 2♭ | B♭ E♭ |
| F major | D minor | 1♭ | B♭ |
| C major | A minor | 0 | – |
| G major | E minor | 1♯ | F♯ |
| D major | B minor | 2♯ | F♯ C♯ |
| A major | F♯ minor | 3♯ | F♯ C♯ G♯ |
| E major | C♯ minor | 4♯ | F♯ C♯ G♯ D♯ |
| B major | G♯ minor | 5♯ | F♯ C♯ G♯ D♯ A♯ |
| F♯ major | D♯ minor | 6♯ | F♯ C♯ G♯ D♯ A♯ E♯ |
| C♯ major | A♯ minor | 7♯ | F♯ C♯ G♯ D♯ A♯ E♯ B♯ |
Each signature belongs to two keys: a major key and its relative minor, which starts three half steps lower (on the sixth note of the major scale) and uses the same notes.
The order of sharps and flats
Sharps are always added in the same order, F♯ C♯ G♯ D♯ A♯ E♯ B♯, and flats in the reverse order, B♭ E♭ A♭ D♭ G♭ C♭ F♭. So you never need to read where each sign sits: count them. Three sharps are always F♯, C♯ and G♯.
Father Charles Goes Down And Ends Battle: sharps. Battle Ends And Down Goes Charles’ Father: flats.
Naming a key in a second
- Sharps: the major key is a half step above the last sharp. Last sharp G♯: A major.
- Flats: the second-to-last flat names the major key. B♭ E♭ A♭: E♭ major. One flat is F major; learn it by heart.
- Minor: go down three half steps from the major key. A major’s relative minor is F♯ minor.
On the circle of fifths, every step clockwise adds a sharp (or takes away a flat), and the new sharp is the leading note of the new key.
Quiz: name the key signature
Ten key signatures in the treble or bass clef. Choose the key, or play its home note on the piano below, a MIDI keyboard or your computer keys (any octave).
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Questions
What is a key signature?
The sharps or flats written right after the clef at the start of every line. They tell you which notes are sharp or flat throughout the piece, and so which key it’s in.
How many key signatures are there?
Fifteen: C major with none, seven with sharps (one to seven) and seven with flats. Three pairs sound the same on the piano: B and C♭ major, F♯ and G♭ major, C♯ and D♭ major. Each signature is shared by a major key and its relative minor.
What is the order of sharps?
F♯, C♯, G♯, D♯, A♯, E♯, B♯ (“Father Charles Goes Down And Ends Battle”). Flats are the same letters backwards: B♭, E♭, A♭, D♭, G♭, C♭, F♭.
How do I tell a major key from its relative minor?
The signature is the same, so look at the music: a minor key usually raises its seventh note with an accidental (G♯ in A minor), and pieces tend to begin and end on the home note or its chord.
Keys, one at a time
Pianomi, a free sight-reading app for piano, brings in key signatures one at a time, G major first, then F, and notices when you play a note as if the key signature weren’t there.