3.2: Minor Key Signatures
Minor key signatures agree with the notes of the natural minor scale. Since the CC natural minor scale had EE♭, AA♭, and BB♭, the key signature of C minor has three flats, written in the order of flats—BB♭, EE♭, AA♭.
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 CC) as the major. We say, “The parallel minor of EE major is EE minor,” and “The parallel major of FF minor is FF 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.
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 (CC) and lowercase for minor (cc). 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 EE♭ major is CCminor because both have three flats in the key signature. Conversely, one could say the relative major of CC minor is EE♭ major. The relative major is three half steps above the relative minor.
Below are the minor key signatures.
Here are circle of fifths diagrams for both major and minor, for comparison.
Writing harmonic minor and melodic minor scales when using minor key signatures requires you to raise scale degrees.
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.