Key signatures in full
Stage 1 taught you what a key signature is — a standing instruction, at the front of every line: these notes are sharp (or flat) every time, all the way through. It also gave you the first three sharp keys. This lesson finishes the job: the full order, why it's that order, and two tricks that name any key signature in a second.
The order never changes
Sharps always arrive in this order: F C G D A E B. Flats always arrive in the exact reverse: B E A D G C F.
A key with three sharps has F♯, C♯ and G♯ — the first three of the list, always in that order. A key with two flats has B♭ and E♭. On the staff they sit in a fixed zig-zag shape, so you learn the picture, not a fresh calculation each time.
Why that order
Each new sharp, as you move to a new key, is a perfect fifth above the last (F → C → G → D…). Each new flat is a perfect fifth below the last. That's not a coincidence — it's because the keys march up (or down) in fifths, and each move forces exactly one new note:
- Going up a fifth (C → G → D…), the note that has to change is the new key's 7th degree — it must be raised to a leading tone. G major's new sharp, F♯, is G major's 7th. D major keeps F♯ and adds C♯, which is D major's 7th.
- Going down a fifth (C → F → B♭…), the new note is the new key's 4th degree, flattened. F major's flat, B♭, is F major's 4th.
Trick 1 — sharp keys
The last sharp is the leading tone. Go up one half step and you're on the tonic.
- Last sharp is F♯ → up a half step → G major.
- Last sharp is C♯ → D major.
- Last sharp is G♯ → A major.
Trick 2 — flat keys
The second-to-last flat names the key.
- Flats B♭, E♭ → second-to-last is B♭ → B♭ major.
- Flats B♭, E♭, A♭ → E♭ major.
- Flats B♭, E♭, A♭, D♭ → A♭ major.
One flat is the exception: B♭ alone is F major — memorise that one, because "second- to-last" needs at least two flats.
The other half of the answer
Every key signature belongs to one major key or its relative minor — the two share all seven notes. One sharp is G major or E minor. No sharps or flats is C major or A minor. Which one a piece is actually in is a listening judgement, and it's the next movement's job. For now: read the signature, name the major possibility, and keep the minor one in mind.
Try it
Name the key signature
- 1
- 2
- 3
- 4
- 5
- 6
Try
Pull up the Minuet in G and Amazing Grace tunes you've played. Look only at the front of each line. Minuet in G (our version) is in D — two sharps, last sharp C♯. Amazing Grace is in G — one sharp. Name each from the signature alone before you look at a single note.
The usual mistake
Working out the scale from scratch to identify a key ("okay, one sharp, F♯, so W-W-H from where…"). You did that once, in The major scale formula. Now use the trick: last sharp plus a half step, or second-to-last flat. It takes a second, and a good sight-reader does it before playing a note.