The natural minor scale follows the formula: T - S - T - T - S - T - T
For example, if we start on the note A, applying the formula gives us the A natural minor scale:
The natural minor scale is commonly used in descending melodies. However, when ascending, it is common to raise the 6th and 7th degrees by one semitone to create a melodic minor scale:
This alteration in the ascending form allows for smoother melodic movement.