Two Sharps, Two Flats & the Relative Minor
Extending key signatures to two sharps and two flats, and the relative minor that shares each major key's signature.
Explainer
Sharps and flats in a key signature always appear in a fixed order, never at random. Sharps: F♯, C♯, G♯, D♯, A♯, E♯, B♯. Flats, in reverse: B♭, E♭, A♭, D♭, G♭, C♭, F♭.
D major has two sharps (F♯, C♯). B♭ major has two flats (B♭, E♭).
Every major key has a relative minor sharing that exact key signature — it starts on the major scale's 6th degree. D major's relative minor is B minor; B♭ major's relative minor is G minor.
A relative minor sounds darker than its major partner, even though the notes available are identical — only the "home" note (the tonic) differs.
Worked examples
D major — two sharps
F♯ and C♯.
D major's relative minor: B minor
Same two sharps (F♯, C♯) — but B is home instead of D.
B♭ major — two flats
B♭ and E♭.
B♭ major's relative minor: G minor
Same two flats (B♭, E♭) — but G is home instead of B♭.