Key Signatures - How to Read Sharps and Flats

At the start of every line of sheet music, right after the clef, you will often see a group of sharps or flats. This is the key signature. It tells you which notes are raised or lowered throughout the piece, so the composer does not have to write an accidental before every F# or Bb. It also tells you - almost - what key the music is in.

This lesson shows you how to read any key signature in a few seconds.

What a key signature does

A sharp or flat in the key signature applies to every note of that letter name, in every octave, for the whole piece (until the key signature changes). If the signature has an F#, every F you read is played as F# unless an accidental (a natural sign, for example) cancels it in that bar.

The key signature always matches the notes of a major scale and its relative minor. That is why there is a limited set of signatures - each one belongs to exactly one major key and one minor key.

The order of sharps

Sharps are always added in the same order:

F# - C# - G# - D# - A# - E# - B#

A key with one sharp has F#. A key with two sharps has F# and C#. A key with three has F#, C# and G#, and so on. You will never see a signature with only C# or only G#.

Mnemonic: Father Charles Goes Down And Ends Battle.

Each new sharp is a perfect 5th above the previous one - the same order as the keys on the sharp side of the circle of fifths.

The order of flats

Flats appear in the reverse order:

Bb - Eb - Ab - Db - Gb - Cb - Fb

Mnemonic: read the sharp sentence backwards - Battle Ends And Down Goes Charles' Father. Many people also remember the first four flats as the word BEAD, followed by G, C, F.

Each new flat is a perfect 4th above (or a perfect 5th below) the previous one.

Naming the major key from the signature

Sharp keys: up a half step from the last sharp

Look at the last sharp (the one furthest to the right) and go up a half step. That note is the major key.

• One sharp (F#): up a half step = G major
• Three sharps (F# C# G#): last is G#, up a half step = A major
• Five sharps (F# C# G# D# A#): last is A#, up a half step = B major

Flat keys: the second-to-last flat

Look at the second-to-last flat - that is the name of the major key.

• Three flats (Bb Eb Ab): second-to-last is Eb = Eb major
• Four flats (Bb Eb Ab Db): second-to-last is Ab = Ab major

This trick needs at least two flats. Just memorise the exception: one flat (Bb) = F major.

No sharps or flats

An empty key signature means C major or A minor.

Minor keys

Every key signature is shared by a major key and its relative minor. To find the minor key, first name the major key, then go down a minor 3rd (three half steps). You can also count up to the 6th note of the major scale.

• Two sharps: D major, down a minor 3rd = B minor
• Two flats: Bb major, down a minor 3rd = G minor
• Four sharps: E major, down a minor 3rd = C# minor

The note you land on must be spelled with the key signature in mind: four sharps include C#, so the relative minor is C# minor, not Db minor.

Major or minor - how to tell

The key signature alone cannot tell you. Look at the music itself:

1. Last note and last chord. Most pieces end on the tonic. A piece with one sharp that ends on E minor is probably in E minor.
2. Raised 7th. Minor-key music usually raises the 7th degree with an accidental (see minor scales). With one sharp, frequent D# accidentals point strongly to E minor.
3. First bars and the bass line. Chords that repeatedly outline the tonic triad are a clue.

All 15 major and 15 minor key signatures

There are seven sharp keys, seven flat keys and one with nothing - 15 signatures, each shared by one major and one minor key.

Enharmonic keys

Three pairs of major keys sound identical but are written differently:

• B major (5 sharps) = Cb major (7 flats)
• F# major (6 sharps) = Gb major (6 flats)
• C# major (7 sharps) = Db major (5 flats)

The same goes for their relative minors (G# minor = Ab minor, D# minor = Eb minor, A# minor = Bb minor). In practice composers choose the version with fewer accidentals, so Db major is far more common than C# major, and Cb major is rare.

Explore all keys and their relationships on the circle:

Writing key signatures correctly

• Sharps and flats are placed in a fixed pattern on the staff, always in the order above, never alphabetically.
• The pattern is the same for every line of music; only the clef changes the vertical position.
• In the treble clef the first sharp sits on the top line (F5); the first flat sits on the middle line (B4).
• A key change mid-piece is shown with a new signature, often after a double bar line. Naturals may be printed to cancel old sharps or flats.

Practice

1. Without looking, write the order of sharps and the order of flats five times each.
2. Name the major and minor key for: 3 sharps, 5 flats, 6 sharps, 1 flat, 4 flats. (Answers: A major / F# minor; Db major / Bb minor; F# major / D# minor; F major / D minor; Ab major / F minor.)
3. Write the key signatures for E major, Ab major, B minor and C minor on staff paper in both treble and bass clef.
4. Take any piece of sheet music and decide whether it is in the major or relative minor key, using the three clues above.

Keep going:

• Drill with key signatures 1 and key signatures 2.
• Print the key signatures chart and the circle of fifths poster.
• Use the interactive circle of fifths and the key finder.
• Look up individual keys, for example D major, Eb major or C# minor.
• Related lessons: circle of fifths, major scale, minor scales, staff and clefs.