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Section 3.2 Minor Key Signatures

Minor key signatures agree with the notes of the natural minor scale. Since the \(\text{C}\) natural minor scale had \(\text{E}^♭\), \(\text{A}^♭\), and \(\text{B}^♭\), the key signature of C minor has three flats, written in the order of flats—\(\text{B}^♭\), \(\text{E}^♭\), \(\text{A}^♭\).
An example showing the lowered 3rd, 6th, and 7th scale degrees placed after the clef as the key signature for the minor key
Therefore, a minor key signature will have three lowered notes—the 3rd, 6th, and 7th—in relation to the corresponding major key signature. We use the term parallel minor when referring to a minor scale that has the same 1st scale degree (in this case \(\text{C}\)) as the major. We say, “The parallel minor of \(\text{E}\) major is \(\text{E}\) minor,” and “The parallel major of \(\text{F}\) minor is \(\text{F}\) major.” One method of figuring out a minor key signature is to add three flats to the parallel major key signature. This is the same as subtracting three sharps.
Adding 3 flats or subtracting 3 sharps to get to the parallel minor key signature from the major key
Note on uppercase versus lowercase: When writing below the five-line staff to designate keys, we will use the shorthand of upper case for major (\(\left.\text{C}\right.\)) and lowercase for minor (\(\left.\text{c}\right.\)). When writing prose, we will use uppercase: C major and C minor.
We use the term relative minor when referring to a minor key that has the same key signature as a major key. For example, the relative minor of \(\text{E}^♭\) major is \(\text{C}\) minor because both have three flats in the key signature. Conversely, one could say the relative major of \(\text{C}\) minor is \(\text{E}^♭\) major. The relative major is three half steps above the relative minor.
Example showing that the relative minor is 3 half steps below the relative major: Eb, D, Db, C
Below are the minor key signatures.
All minor key signatures are shown
Here are circle of fifths diagrams for both major and minor, for comparison.
Figure 3.2.1.
Figure 3.2.2.
Writing harmonic minor and melodic minor scales when using minor key signatures requires you to raise scale degrees.
Example showing raising of 7th scale degree of the harmonic minor when using minor key signature, and raising 6th and 7th scale degrees of ascending melodic minor when using minor key signature
Compositions in minor typically do not strictly use only one of the three minor scales, however. The three minor scales are distillations of composers’ actual practice.
The opening two measures of Bach’s C Minor Invention, which uses natural minor then harmonic minor
Figure 3.2.3. J.S. Bach, C Minor Invention
The opening eight measures, which show the natural minor scale in the first six and the harmonic minor scale in the last two
Figure 3.2.4. Mozart, Symphony No. 40 in G Minor, K. 550, 1st movement
TThe opening three measures, which uses harmonic minor then melodic minor
Figure 3.2.5. J.S. Bach, Well-Tempered Clavier, Book One, Fugue 2 in C Minor