Key signatures: G major and F major

A key signature is the sharps or flats at the start of every line, and it holds for the whole piece in every octave. One sharp, on F, is G major: every F is F sharp. One flat, on B, is F major: every B is B flat.

A key signature is the group of sharps or flats at the start of every line of music. It holds for the whole piece, in every octave. One sharp, on F, means G major: every F is played as F sharp. One flat, on B, means F major: every B is played as B flat. Look at it before the first note, every time.

G major: one sharp

The G major key signature is a single sharp (♯) drawn on an F:

• Treble staff: on the top line, F5.
• Bass staff: on the fourth line, F3, between the bass clef's dots.

It means every F is F sharp: the F on the top line, the F in the bottom space, the Fs above and below the staff. F sharp is the black key just below G, the first of a group of three black keys.

The G major scale is G A B C D E F♯ G. Only the F changes.

F major: one flat

The F major key signature is a single flat (♭) drawn on a B:

• Treble staff: on the middle line, B4.
• Bass staff: on the second line, B2.

It means every B is B flat. B flat is the black key just below B, the last of a group of three black keys.

The F major scale is F G A B♭ C D E F. Only the B changes.

Reading notes in a key

• A sharp or flat doesn't move the note on the staff. F sharp sits on the same line or space as F; it is played on a different key. The staff says which letter; the key signature says which key of that letter.
• The signature is not repeated beside each note. That is its whole point: it is written once, at the start of each line.
• A natural sign (♮) beside a note cancels the key signature for that note, until the end of the bar.
• An accidental (a sharp, flat or natural written beside a note) lasts until the end of its bar, on that line or space.

How the hand finds the black key

In G major, the right hand often plays in a G position: thumb on G, fingers on A, B, C, D. F sharp is then just below the thumb, or reached by the fourth finger from higher up. In F major, B flat falls under the fourth finger in an F position (thumb on F: F G A B♭ C).

Major or minor?

Every key signature is shared by a major and a minor key. One sharp is G major or E minor; one flat is F major or D minor. The music itself tells you which: a piece in E minor usually begins or ends on E and often has D sharps written in. Octotune's path stays with the major keys.

Common mistakes

• Playing F natural in G major. The most common mistake of all: the sharp isn't printed next to the note. Look at the key signature before you start.
• Thinking the sharp only applies to one F. It applies to every F, in every octave.
• Thinking a sharp moves the note on the page. Same line, different key.
• Forgetting the bass clef. The left hand's Fs are sharp in G major too.

How to practise

1. Circle every F on a page of music in G, or every B in F, before you play.
2. Play the scales hands separately: G major with its F sharp, F major with its B flat.
3. Find F sharp in every octave, then B flat in every octave.
4. Play a simple piece in each key. The Minuet in G (the one long credited to Bach, now to Christian Petzold) is the classic for G major; Yankee Doodle works well for F.

How Octotune helps

Unit 10 of Octotune's adult path is keys: a concept card on key signatures, then F sharp met in both clefs, cards and pages written in G, the Minuet in G and Schumann's music; then B flat, pages in F, Yankee Doodle and The Happy Farmer. Note cards in a key only ever show notes that belong to that key. In the app's coach, a black key is spelled for the key you are in: B flat in F major, never A sharp. Open Octotune.

Next: Triads and the I, IV and V chords.

Practise it: Unit 10, Keys of G and F

The Octotune team · Updated 23 September 2026