Key signatures: how to read every key
A key signature is the group of sharps or flats at the start of each line of music. It tells you which notes are raised or lowered all through the piece, and it shows the key. Each key signature fits one major key and one minor key.
A key signature is the set of sharps or flats printed right after the clef at the beginning of every staff. It tells the player which notes are sharp or flat throughout the piece, so that the sharps and flats do not have to be written beside every note. It also tells you the key of the music, which is the home note and the scale the music is mostly built from.
What does a key signature do?
A key signature applies to every note with that letter name, in every octave, from the start to the end of the piece or until a new key signature appears. If the signature has an F♯, then every F, high or low, is an F♯. This saves a lot of writing, and it keeps the page easy to read.
Accidentals written beside a single note, like an extra sharp or a natural sign, work only for that note and for the rest of that measure. A new measure goes back to the key signature. See sharps, flats and naturals for the details.
The order of sharps and flats
Sharps and flats always appear in the same order, and always in the same places on the staff. The order of sharps is F C G D A E B. The order of flats is the reverse: B E A D G C F. A key with three sharps has F♯, C♯ and G♯. A key with three flats has B♭, E♭ and A♭.
| Accidentals | Order |
|---|---|
| Sharps | F C G D A E B |
| Flats | B E A D G C F |
Memory trick: For sharps, Father Charles Goes Down And Ends Battle. For flats, read the same phrase backward: Battle Ends And Down Goes Charles' Father.
How to find a major key from the key signature
There is a quick rule for each kind of signature. With sharps, find the last sharp in the list, and the key is a half step above it. With flats, find the next-to-last flat, and that flat's name is the key. One flat is a special case: it is always F major.
| Signature | Rule | Major key |
|---|---|---|
| 1 sharp (F♯) | Last sharp is F♯, half step up | G |
| 2 sharps (F♯ C♯) | Last sharp is C♯, half step up | D |
| 3 sharps (F♯ C♯ G♯) | Last sharp is G♯, half step up | A |
| 1 flat (B♭) | Special case | F |
| 2 flats (B♭ E♭) | Next-to-last flat is B♭ | B♭ |
| 3 flats (B♭ E♭ A♭) | Next-to-last flat is E♭ | E♭ |
No sharps and no flats means C major (or A minor). Seven sharps is C♯ major, and seven flats is C♭ major. Every major key has its own signature, and every one can be read with these rules.
The minor keys
Every key signature fits two keys: a major key and its relative minor. The minor key's tonic is three half steps below the major key's tonic. G major and E minor share one sharp. D major and B minor share two sharps. F major and D minor share one flat. To read a minor key, find the major key first, then go down to its relative minor.
One caution: in minor keys, the signature fits the natural minor scale. The raised seventh in harmonic and melodic minor appears as an accidental in the music, not in the key signature.
Sharp keys and flat keys together
There are fifteen key signatures in all: no accidentals, one to seven sharps, and one to seven flats. Because the keys at the far ends overlap, three pairs of keys sound the same but are written differently: B and C♭, F♯ and G♭, C♯ and D♭. Those are enharmonic keys. The circle of fifths arranges all of them in a single ring.
| Sharps | Major key | Flats | Major key |
|---|---|---|---|
| 0 | C | 0 | C |
| 1 | G | 1 | F |
| 2 | D | 2 | B♭ |
| 3 | A | 3 | E♭ |
| 4 | E | 4 | A♭ |
| 5 | B | 5 | D♭ |
| 6 | F♯ | 6 | G♭ |
| 7 | C♯ | 7 | C♭ |
Practice tips
- Drill the order of sharps and flats until you can say it forward and backward.
- Look at a piece and name its key before you play.
- Write out the signatures from memory, in the right places on the staff.
- Try sorting a set of key signature cards in the order of the circle of fifths.
- Use the key page for each scale, such as G major, to check your answers.
Once you know a key signature, you also know which notes to expect. The major scales page shows each scale's spelling, and the key pages list the chords as well.
Every key signature
| Key signature | Major key | Minor key |
|---|---|---|
no sharps or flats | C major | A minor |
one sharp: F♯ | G major | E minor |
two sharps: F♯ and C♯ | D major | B minor |
three sharps: F♯, C♯ and G♯ | A major | F♯ minor |
four sharps: F♯, C♯, G♯ and D♯ | E major | C♯ minor |
five sharps: F♯, C♯, G♯, D♯ and A♯ | B major | G♯ minor |
six sharps: F♯, C♯, G♯, D♯, A♯ and E♯ | F♯ major | D♯ minor |
seven sharps: F♯, C♯, G♯, D♯, A♯, E♯ and B♯ | C♯ major | A♯ minor |
one flat: B♭ | F major | D minor |
two flats: B♭ and E♭ | B♭ major | G minor |
three flats: B♭, E♭ and A♭ | E♭ major | C minor |
four flats: B♭, E♭, A♭ and D♭ | A♭ major | F minor |
five flats: B♭, E♭, A♭, D♭ and G♭ | D♭ major | B♭ minor |
six flats: B♭, E♭, A♭, D♭, G♭ and C♭ | G♭ major | E♭ minor |
seven flats: B♭, E♭, A♭, D♭, G♭, C♭ and F♭ | C♭ major | A♭ minor |
Check yourself
1. What is the order of sharps?
Answer: F C G D A E B. Each new sharp is a fifth above the last.
2. How do you find the major key from a key signature with sharps?
Answer: Go a half step above the last sharp. The last sharp is the leading tone, one half step below the tonic.
3. Which major key has one flat?
Answer: F major. One flat is a special case: F major.
4. A key signature with 2 flats is the key of which major scale?
Answer: B♭ major. The next-to-last flat of B♭ and E♭ is B♭.
5. Which minor key has the same signature as G major?
Answer: E minor. The relative minor is three half steps below the major tonic.