Armadura de Clave por Tonalidade

Key signatures: rule and example

A key signature tells you which sharps (#) or flats (♭) belong to a key. The sharp keys climb the circle of fifths: G has 1#, D 2#, A 3#, E 4#, B 5#, F# 6#, C# 7#. Going the other way you pick up flats: F 1♭, B♭ 2♭, E♭ 3♭. C major carries no accidentals at all, and neither does its relative minor three semitones down, A minor.

Context and applications

The key signature sits right after the clef on every staff, sparing the composer from scribbling an accidental next to every note. In sight-reading, one glance gives away the tonal center. For transposition, you shift every note by the same interval and grab the matching signature. When composing, it lets you settle on a key that suits the instrument's range. And in harmonic analysis, the very same II–V–I cadence wears a different face in C, F, or B♭. Every major key shares its signature with a relative minor.

FAQ

How do I find the relative minor? Drop three semitones, or climb a minor sixth, whichever you prefer. C major → A minor, G major → E minor, F major → D minor.

Order of sharps and flats? Sharps line up as F–C–G–D–A–E–B. Read that backwards and you get the flats: B–E–A–D–G–C–F.

What is the circle of fifths? It's a diagram that lays out the 12 keys a fifth apart. Step clockwise and you add a sharp; step counterclockwise and you add a flat.

Why do C# major and D♭ major sound the same? They're enharmonic equivalents, the same pitches once you're in equal temperament. C# carries 7 sharps while D♭ gets by with 5 flats, so composers just pick whichever signature is easier on the eye.