Question: Which minor scale... natural, harmonic, or melodic, should I be practicing on when playing the major scale, then to its relative minor scale?Richard (North Carolina, USA)
Albert's reply: While we need to know all three forms of the minor scale, if you only practice one it should be harmonic minor. In actual pieces of music, harmonic minor is more common than melodic minor.
Natural minor occurs comparatively infrequently, since the leading tone (scale degree 7) needs to be raised in order to form the essential dominant harmony, and it is not raised in natural minor.
For those unfamiliar with natural minor, let's use A minor as an example. A minor is the relative minor of C major, meaning that they share a key signature. In this case, there are no sharps or flats in the key signature.
A natural minor is A B C D E F G A.
A harmonic minor is A B C D E F G# A.
G is the seventh scale degree, and in the harmonic minor it is raised to G-sharp, the leading tone to A.
As for practicing scales, once you're familiar with all of them I recommend practicing not relative keys, but parallel keys. Thus, I recommend practicing C major, C minor, then D-flat major, C-sharp minor, then D major and D minor, etc.
Even better, save C major for the end of your scales routine... it's the hardest!