Natural minor
The Aeolian minor scale.
What it means
Natural minor is the minor scale without any alteration: semitone steps between the second and third and between the fifth and sixth degrees, the seventh degree a whole tone below the tonic. It corresponds to the Aeolian mode and contains exactly the notes the key signature indicates — no raisings within the bar.
Musical use
Every major key has a relative minor with the same key signature, whose tonic lies a minor third lower: A minor to C major, E minor to G major. Which of the two is meant is revealed not by the key signature but by the music — the closing note, the emphasis on the tonic, and the occurrence of a raised leading tone.
Precisely this leading tone is absent from the natural form. For the cadence of major-minor tonality it is indispensable, which is why it is obtained by raising the seventh degree — from this the harmonic and melodic forms arise. The natural form nonetheless remains the stock of notes of the key and determines which notes the key signature contains.
Tonally, natural minor sounds softer and more archaic than the altered forms, because it lacks the goal-directed tension. It is therefore widespread in folk music, folk, and popular music, where minor often appears without a leading tone.
Natural minor is to be distinguished from Dorian, which differs only in the higher sixth degree.
In jazz theory this scale is also called Aeolian. Since the leading tone is absent, the dominant is a minor chord and the cadence seems less goal-directed. For the cadence, classical harmony therefore raises the seventh degree. In folk music, rock, and pop, by contrast, natural minor is often found unaltered, for instance in chord progressions with a minor chord on the fifth degree. In English it is called natural minor.
Performance practice
In a minor piece, check first whether and where the seventh degree is raised — this decides the phrasing. Where the leading tone is absent, do not play toward a cadence the music does not provide for. And resist the habit of involuntarily raising the seventh degree while practising.