Why G major has one sharp
A major scale is not a set of notes you memorise — it's a fixed pattern of steps, the same shape wherever you start it. Start that shape on G and exactly one note has to be bent to fit. That note is F♯, and that's the entire reason G major's key signature has one sharp and nothing else.
Walk the pattern from G
The major-scale pattern is whole–whole–half–whole–whole–whole–half (W-W-H-W-W-W-H). Lay it over the natural notes starting on G and check each step against what the letters give you naturally:
| Step | Needs | Natural notes give | Fix? |
|---|---|---|---|
| G → A | whole | whole | — |
| A → B | whole | whole | — |
| B → C | half | half | — |
| C → D | whole | whole | — |
| D → E | whole | whole | — |
| E → F | whole | half | raise F → F♯ |
| F♯ → G | half | half | — |
Every step already fits except E → F. Naturally E to F is a half step, but the pattern needs a whole step there — so F is raised to F♯, which also makes the last step (F♯ → G) a half step, exactly as the pattern wants. One adjustment, and the shape is satisfied.
Hear why it has to be F♯
Play the scale as written. Now play this — the same scale, but with an F natural (a low 2nd finger) instead of the F♯:
Listen to that F♮: it sits a whole step below the top G, so the climb to the tonic sags instead of leaning in. The F♯ is what gives a major scale its pull home. Your ear will tell you the F♮ is wrong before your theory does.
Where this sits
This is the derivation behind the key signature you met in Stage 1. It isn't arbitrary and it isn't worth memorising as a fact — it falls straight out of the pattern. Do the same walk from D and you'll find you need F♯ and C♯; from A, three sharps; and so on. That growing stack of sharps, always added in the order F–C–G–D–A–E–B, is the circle of fifths, which gets its own lesson.
There's a reason a beginner meets G major first on the violin and not, say, on the piano, where C major is the obvious start. Your open strings — G, D, A, E — are themselves a stack of perfect fifths, and G major lies right under the first-position hand. That's why so much early violin repertoire is written in G, D and A.
One thing major does not mean: "happy." It names this interval structure, nothing else. Whether a piece in G major sounds bright, grieving, tense or calm is decided by its melody, harmony, tempo and touch — the key alone decides none of it.