Key signature · 0
C major key signature and A minor
C major and its relative minor, A minor, share a key signature of no sharps or flats.
- Sharps0
- Whichnone
- Relative minorA minor
- Home chordC–E–G
The key signature
There’s nothing after the clef: no sharps and no flats. Every note is played as written, on the white keys, unless an accidental appears beside it.
How to recognise it quickly
No sharps or flats at all: C major, or A minor. It’s the only signature that’s empty.
The C major scale
C – D – E – F – G – A – B – C. All white keys. Its home chord is C–E–G.
More on this key: the C major scale with fingering · the C major chord
A minor, the relative minor
A minor uses the same white keys, starting from A, the sixth note of C major: A – B – C – D – E – F – G – A. That’s the natural minor scale. Its home chord is A–C–E.
Pieces in A minor usually raise the seventh note, G, to G♯ (the harmonic minor), so it leads up to A. That G♯ is written as an accidental, not in the key signature: the sharp beside the note is often the quickest clue that a piece is in A minor rather than C major. Pieces also often begin or end on A or its chord.
More on this key: A minor natural minor · A minor harmonic minor · the A minor chord
Music in C major and A minor
Mozart’s Piano Sonata in C major, K. 545, the one many pianists learn first, is in C major.
Beethoven’s Für Elise and Mozart’s Rondo alla Turca (the Turkish March) are both in A minor.
On the circle of fifths
One sharp more is G major, a fifth higher; one flat more is F major, a fifth lower. Keys next to each other on the circle of fifths share all but one note, which is why music in C major moves to them most easily.
C minor, with the same home note but a minor scale, has a different key signature: three flats, the same as E♭ major.
Quiz: name the key signature
Ten key signatures in the treble or bass clef, from all fifteen. Choose the key, or play its home note on the piano below, a MIDI keyboard or your computer keys (any octave).
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Questions
How many sharps are in C major?
C major has no sharps or flats: it uses only the white keys.
What is the relative minor of C major?
A minor. It shares the key signature (no sharps or flats) and starts on the sixth note of the C major scale, three half steps below C.
What are the notes of the C major scale?
C, D, E, F, G, A, B, C.
Which key has no sharps or flats?
C major and its relative minor, A minor.
Keys, one at a time
Pianomi, a free sight-reading app for piano, brings in key signatures one at a time and notices when you play a note as if the key signature weren’t there.