The Complete Idiot''s Guide to Music Theory

Part 1:
Tones
Minor Keys
The key signatures used to indicate major keys also can represent natural minor
keys. As you remember from Chapter 3, a natural minor scale is based on the
same notes as a major scale, but starts on the sixth note of the scale. This same
method applies to keys, so that (for example) the key of A minor uses the same
notes—and the same key signature—as C major.
The following table shows the 15 minor keys, with their corresponding key sig-
natures and scales.
The 15 Minor Keys
Same as This
Scale
Notes
Major Key
A minor
C Major
A-sharp minor
C-sharp Major
B-flat minor
D-flat Major
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How can you quickly determine which key signature you’re looking at?
It depends on whether the key signature contains sharps or flats.
If the key signature includes flats, the key (no pun intended) is to look at
the next-to-last flat—the one that’s next to the farthest one on the right.
This note determines the key signature.
For example, if a key signature has two flats, you look at the next-to-last flat and
determine that the key is B-flat, which it is. If the key signature has three flats, you
look at the next-to-last flat, and determine that the key is E-flat. It’s pretty easy.
But what do you do if there’s only one flat? There’s no next-to-last flat! For the key
signature with a single flat, the key is F. You’ll have to memorize that one, as you
will the key with no flats or sharps—which is the key of C.
If the key signature includes sharps, the method is different. What you want to
remember here is that the last sharp in the key signature represents the seventh
degree of that particular scale, so that the tonic of the scale is the next note up.
In other words, look at the last sharp and the next note up is the key.
Take, for example, the key signature with one sharp. That sharp is on the note F-
sharp, so the next note up tells you that the key is G. If the key signature has two
sharps, the last one is on the note C-sharp, and the next note up is D—which is
your key. And so on for all the other sharp key signatures.