How to memorise key signatures

There are thirty key signatures to know and you do not have to memorise thirty things. Two shortcuts cover almost all of them.

First: the order never changes

Sharps always appear in this order:

F♯ C♯ G♯ D♯ A♯ E♯ B♯

Flats appear in exactly the reverse:

B♭ E♭ A♭ D♭ G♭ C♭ F♭

A signature with three sharps is always F♯, C♯, G♯. Never some other three. So the only thing to identify is how many, and the rest follows.

This is not a convention someone invented — each accidental is a fifth above the last, which is what the circle of fifths draws.

Common mnemonics: Father Charles Goes Down And Ends Battle for sharps, and the same sentence backwards — Battle Ends And Down Goes Charles' Father — for flats.

Trick one: sharps — last sharp, up a semitone

Find the last sharp in the signature and go up one semitone. That is the major key.

• Last sharp is F♯ → up a semitone is G → G major
• Last sharp is C♯ → D major
• Last sharp is G♯ → A major

Trick two: flats — the second-to-last flat

The major key is the second-to-last flat, read off directly.

• Flats are B♭, E♭ → second-to-last is B♭ → B♭ major
• Flats are B♭, E♭, A♭ → E♭ major
• Flats are B♭, E♭, A♭, D♭ → A♭ major

The three you memorise

The tricks fail in exactly three places, so learn these outright:

• No accidentals → C major
• One flat → F major (there is no second-to-last flat)
• One sharp → G major (works with the trick, but it is worth knowing instantly)

Going the other way

To find the signature from the key name, count round the circle of fifths from C. Each step clockwise adds a sharp, each step anticlockwise adds a flat.

C(0) → G(1♯) → D(2♯) → A(3♯) → E(4♯) → B(5♯) C(0) → F(1♭) → B♭(2♭) → E♭(3♭) → A♭(4♭) → D♭(5♭)

Note that the sharp keys are themselves in the sharp order shifted — G D A E B — which is another way of saying the whole system is one pattern.

Finding the minor key

Every signature serves two keys. To get the minor, go down a minor third from the major — three semitones.

• C major → A minor
• G major → E minor
• E♭ major → C minor

Which of the two a piece is actually in is decided by the music, not the signature. Look at the last bass note, and look for a raised seventh appearing as an accidental — a piece in A minor that keeps writing G♯ is announcing itself. See relative and parallel keys.

How to practise this

Flashcards work and are dull. Two better options:

Read real music. Open any piece, name the key before you play, then check whether the music agrees. You get context, which flashcards do not give.

Drill under time pressure. Recognition needs speed, and speed needs a clock. Tomus — our app — has a Key Signatures game that shows a signature and asks for the key against a timer, which is the same drill with the tedium removed.

Every signature is tabulated with its notes and chords in the key reference.