Tendency Tones and Minor Scales

[Theory on the Web - copyright 2000 Robert J. Frank]

Tendency Tones and Minor Scales

As we saw in the prevous section on scales, the major scale has the following pattern of whole and half-steps :

C Major Scale

Notice how strongly the second to the last note, the B, needs to resolve to the tonic C. When a certain tone has a strong pull toward another, we call it a tendency tone. Notes that are only a half-step apart commonly function as tendency tones. Notice that the 4th scale degree, F, also is only a half-step from E. However, since scale degree 7 pulls toward the most stable pitch, the tonic, it is the most important tendancy tone.

In a natural minor scale, however, the seventh scale degree is not a half-step from tonic, but rather a whole step (see the following figure). This reduces the "pull" toward the tonic.

Because the resolution of the half-step between scale degree 7 and tonic is so important to tonal music, composers have frequently used a raised scale degree 7 in the minor scale. This also supports the harmonic function in minor keys (this will be discussed in the later section on harmonic function). For this reason, it is called the harmonic minor scale. A harmonic minor scale is a natural minor scale with a raised scale degree 7.

Notice in the above example that by raising the scale degree 7, the unusual interval of an augmented second is formed between scale degrees 6 and 7. The half-step between scale degrees 6 and 5 cause scale degree 6 to behave as a tendency tone, resolving to scale degree 5. As a result, melodies in minor keys frequently avoid the harmonic minor scale, because of this difficult interval. Instead, composers will usually alter the scale degree 6 on ascending passages, and use the natural minor scale on descending passages. This form of the minor scale is called the melodic minor scale.

A melodic minor scale raises scale degrees 6 and 7 on the way up, and lowers them back to their natural minor form on the way down. This results in a scale that keeps the half-step between scale degree 7 and tonic, yet avoids augmented intervals. The following is a melody that uses the melodic minor scale. Notice that every time that scale degrees 6 or 7 continue upward, they are raised. Whenever they resolve downward, they are lowered.

Relationships Between Major and Minor Keys

As we noted in the section on key signatures, minor scales built on the sixth scale degree of a major scale have the same key signature. This is called the relative minor to the major key (or relative major to the minor key, depending upon from which you are starting.) For example: in F Major, the sixth scale degree is the pitch class "D":

F Major (1 flat) = d minor relative minor

A second type of relationship exists when the tonic is the same: i.e. C Major and c minor. This is called the parallel minor (or major). An easy way to find the key signature for the parallel minor of any major key is to add 3 flats (or remove 3 sharps) from the key signature. For example: