Natural minor and relative keys
Build a natural minor scale and find the minor key that shares a major key's key signature.
The natural minor
Play the white keys not from C but from A up to the next A. The notes are those of C major, but the tonic is different, and the scale sounds different: darker, sadder. This is the natural minor, the A minor scale.
The natural minor scale on A: white keys only, too
A minor on the keyboard
The natural minor formula: tone, semitone, tone, tone, semitone, tone, tone. The semitones are between degrees II and III and between V and VI. The main difference from major is degree III: in minor, I to III is a tone and a half (a minor third); in major it is two tones (a major third).
Practice: Major or minor?
Practice: Melodic dictation in A minor
Relative keys
A minor and C major share the same notes and the same key signature: none. Such keys are called relative. Every major key has a relative minor: its tonic is degree VI of the major, a minor third (three semitones) below the major tonic.
G major (one sharp) goes with E minor; F major (one flat) with D minor.
E minor: the key signature of G major, F♯
D minor: the key signature of F major, B♭
To find the relative minor, go down three semitones from the major tonic: C → A, G → E, F → D.