How the minor scale is generated

The minor scale is a modification of the major scale. To understand the principle behind that modification, let's go back to the way the major scale is generated, which you saw in Lesson 1 of this part.

First, a review: three major triads

• The major scale is generated by three generating tones, the tonal notes, which are F, C and G in C major.
• Each one carries a major triad, that is, a major third and a perfect fifth above a bass note, and the three triads follow one another a perfect fifth apart.
• When you write the tones of these three triads stepwise, starting from C, you get the C major scale.

In minor, the three thirds are lowered

Now here is what happens in the minor scale: the third of each of the three generating triads is lowered a chromatic half step, or chromatic semitone in British English. The third becomes minor, and the major triad becomes a minor triad, made of a minor third and a perfect fifth above a bass note.

If you write these tones stepwise, starting from C, you get this scale:

The problem with the 7th degree

This scale has two weaknesses, and they are worth understanding:

• the 7th degree, B♭, lies a whole step below the 8th, so it loses its function as a leading tone (a leading note, in British English), and it is called the subtonic;
• it also contains exactly the same tones as the E♭ major scale, which creates ambiguity.

The classical masters use this scale often, especially in descending melodic lines. Usually, though, it is replaced by another minor scale in which the 7th degree is raised a chromatic half step, and that gives it back its leading-tone function.

The augmented second

Because of this alteration, an augmented second appears between the 6th and 7th degrees, from A♭ to B♮. It is made of a whole step plus a chromatic half step, which makes three half steps on the keyboard. Listen: this interval gives the scale its characteristic color.

The three forms of the minor scale

In the minor scale with a leading tone, the 6th degree is often raised a chromatic half step as well, especially going up, to avoid the augmented second. It then forms a major sixth with the tonic and is no longer a modal note. So there are really three minor scales, and this table puts them side by side:

They are sometimes called “descending melodic minor” and “ascending melodic minor” because classical practice goes up with the raised sixth and seventh and comes back down without them. The harmonic form is rarely used melodically by the classical composers, but it contains every note of the essential harmonies of minor. The modal weight of the minor sixth and the tonal weight of the leading tone made it the standard form of the minor scale, and this is the one Danhauser compares with the major scale.

In the next lesson, you'll see how every major scale is paired with a minor scale that shares its key signature: its relative key.