What a key signature tells you
The key signature is the group of sharps or flats written at the start of every line, right after the clef. It says which notes are raised or lowered all the way through the piece, so you do not need an accidental in front of each one. It also tells you the key.
Four things to know
- How many. Count steps from C on the circle of fifths: G has 1 sharp, D has 2, A has 3. F has 1 flat, B♭ has 2, E♭ has 3.
- Which ones. Sharps arrive in the order F C G D A E B, flats in the order B E A D G C F. A key with n sharps has the first n.
- The key from sharps. The last sharp is a half step below the key note. Last sharp G♯? The key is A.
- The key from flats. The second-to-last flat is the key. Flats B♭ E♭ A♭? The key is E♭.
Every key signature also belongs to a minor key: the relative minor, three half steps below the major key. A minor shares C major's signature of no sharps or flats.
The quiz drills these four skills one by one. For the full chart, see key signatures and the circle of fifths trainer. Practise reading them on a staff in staff reading.
Frequently asked questions
How do I memorise key signatures?
Learn the circle of fifths: each step clockwise adds one sharp (C, G, D, A, E, B, F♯, C♯) and each step anticlockwise adds one flat (C, F, B♭, E♭, A♭, D♭, G♭, C♭). Then learn the order the accidentals arrive in: sharps F C G D A E B, flats B E A D G C F.
What is the order of sharps and flats?
Sharps are added in the order F C G D A E B. Flats are added in the opposite order, B E A D G C F. A key with three sharps has the first three: F♯, C♯ and G♯.
How do I find the key from the key signature?
For sharps, the last sharp is the leading note, a half step below the key: with F♯ C♯ G♯ the last is G♯, so the key is A major. For flats, the second-to-last flat names the key: with B♭ E♭ A♭ the second-to-last is E♭, so the key is E♭ major. The only exception is one flat, which is F major.
How do I tell major from minor?
A key signature fits two keys, a major key and its relative minor, which starts three half steps lower. A minor has the same signature as C major (none). To decide which one a piece is in, listen for the note that feels like home, or look at its first and last chord.
How many key signatures are there?
There are 15 for major keys and 15 for minor keys, each with 0 to 7 sharps or flats. F♯ major and G♭ major, B and C♭, and C♯ and D♭ sound the same, so in practice most music uses 12.