Apart from major keys, the other basic tonality used in western music is a minor key. Minor keys are often said to have a sadder or darker sound than major keys. Songs in a minor key use notes taken from a minor scale. There are three types of minor scale - the natural minor scale, the harmonic minor scale and the melodic minor scale. The following diagram shows is the A natural minor scale. It contains exactly the same notes as the C major scale. The difference is that it starts and finishes on an A note instead of a C note. The A note then becomes the key note. The A natural minor scale is easy to learn - it is simply the notes of the musical alphabet.
Here is the A natural minor scale played with both hands - first in eighth notes over two octaves and then in sixteenth notes over three octaves.