Lesson 21: Key Signatures and the Circle of Fifths

• Read a key signature without thinking about it.
• Name the sharps or flats in any common key.

• Lessons 11 and 14 — sharp and flat keysigs in practice.

• Key signatures.
• Circle of fifths.
• Key relationships.

A key signature is a contract: these notes are altered unless I say otherwise.

A key signature sits between the clef and the time signature; it says “every F is sharp” or “every B is flat” without writing the accidental in front of each note. You have been reading them for ten lessons already. This lesson gives them their formal name and shows where every key sits in relation to every other.

The circle

Move up by a perfect fifth from C: C → G → D → A → E. Each step adds one sharp. Move down by a fifth: C → F → Bb → Eb. Each step adds one flat. C major sits at the top with zero accidentals; the keys spread outward in both directions.

C major / A minor

No sharps or flats.

G major / E minor

One sharp: F#.

D major / B minor

Two sharps: F#, C#.

A major / F# minor

Three sharps: F#, C#, G#.

F major / D minor

One flat: Bb.

Bb major / G minor

Two flats: Bb, Eb.

Eb major / C minor

Three flats: Bb, Eb, Ab.

Now play these

One piece in each of three keys, to fix the habit of reading the key signature first.

Ode to Joy · C major

No accidentals. The home key.

Scarborough Fair · G major

One sharp. Watch every F.

Pavane: Belle qui tiens ma vie · F major

One flat. Watch every B.

When you can name the sharps or flats of C, G, D, F, and Bb major from memory without pausing, move on to Lesson 22.