piano scale
A natural minor
A1B2C♭3D4E5F♭6G♭7
The major scale started from its sixth degree: same seven notes, a different centre of gravity.
Written out
Every accidental is written in, rather than left to a key signature, so the letters can be read one at a time.
The step pattern
AWBHCWDWEHFWGWA
What is true of it
A natural minor is A, B, C, D, E, F and G, and back to A.
Its steps are W – H – W – W – H – W – W, where W is a whole step and H a half.
It uses no sharps and no flats at all: seven letters, seven white keys.
On the same tonic, A harmonic minor differs from it by exactly one note.
Chords made only of these notes
Found by testing every chord in the catalogue against these 7 sounds, not chosen.