The key signature · From Zero to Mozart

Right after the clef, before the music starts, you'll often see one or more sharps (or flats). That's the key signature — a standing instruction: these notes are sharp every time, in every octave, for the whole piece, unless a later mark cancels one. It saves writing the sign on every single F.

66 bpm

One sharp after the clef. Every F in this piece is now F sharp — including this one, written with no sign of its own. This is the scale of G major.

One sharp is G major

The single sharp is always F♯, and it means G major — the key of Ode to Joy, of the open strings ringing, and (as it happens) of the Mozart concerto this course points toward.

Spot the F that's really F♯

58 bpm

One sharp in the signature. There's one F in this line, written with no sign of its own. Find it, and know it's F♯ — high 2 — before you reveal.

The same phrase, two keys

58 bpm

In G major (one sharp): D E F♯ G, all on the D string. The F is F♯.

58 bpm

The same shape (do–re–mi–fa) in A major (three sharps): A B C♯ D, on the A string. The reading rule is identical — the key signature just moved the sharps, and the hand shifted a string over.

The order of sharps

They always arrive in the same order — F C G D A E B — and each key adds the next one:

Sharps	Key	Which sharps
0	C major	—
1	G major	F♯
2	D major	F♯ C♯
3	A major	F♯ C♯ G♯

That order — F C G D A E B — is itself a chain of ascending fifths, and each new key is a fifth above the last. You'll build the whole logic in Stage 4; for now, learn the top three, because G, D and A are the keys that fall under the first-position hand (the same open-string reason the violin is tuned G–D–A–E).

The usual mistake

Playing F♮ in a sharp key because there's no ♯ printed next to that particular note. The signature already said it — once, at the front, for good.

Try

Take the G-major line above. Point at every F and say "F sharp" before you play. Then play it again with a plain F on purpose, and hear how wrong it sounds against the rest.