Lesson 7: 調號 (Key Signatures)

In Lesson 4, we learnt that the black keys can be represented on the staff using sharps (#) or flats (b). And the reason for having sharps and flats is that white keys alone cannot be used to represent all the scales in different keys.

So, how many different keys are there in total? By looking at the keyboard again, we see that there are 7 white keys and 5 black keys in each octave. Therefore, there are 7+5=12 different keys in total. Each of these keys are named by the note it starts with. E.g. the key that starts with C is called C Major.

Each major (大調) key has a unique key signature (調號), with a unique number of sharps or flat. By "unique", it means that e.g. A major's key signature has 3 sharps, so whenever you see 3 sharps, it must be A major and nothing else. This will be slightly different when we learn about the minors (小調), but let's not worry about them yet.

In order to tell how many sharps/flats each of the 12 keys have, we have to construct their scales.

• Starting with C major (C大調), which has no sharp nor flat. To construct the next scale, we go to the 5th note in the scale of C major: G.
• The key that starts with G is G major (G大調), and you will find that it will have one sharp (F#) if you construct its scale using the pattern shown in Lesson 4.
• To construct the next scale, we, again, go to the 5th note of the scale of G major: D.
• Repeat this process and you will find that all 12 keys will be constructed. (It is easier to do this exercise at a keyboard/piano.) Some of them will have sharps in their key signatures, and some will have flats.

The process of constructing scales can be summarized by the Circle of Fifths (調的五度循環):

The logic behind the Circle of fifths is that when you go clockwise, the next key is always a perfect 5th from the current key. This is the more technical way of saying that the next key always starts on the 5th note of the current key. Note that the keys on the right of the Circle of fifths are the keys with sharps in their key signatures, and the ones on the left are those with flats in their key signatures. As you may notice that F# (or Gb) major is at the bottom of the circle, because its key signature can be either 6 sharps or 6 flats. This is the theory behind differnt keys, but the most important thing is to remember ALL the key signatures, which are summarized below:

Questions that you should be able to answer by the end of this lesson:

1. Can you name the associated major key by looking at the key signatures?
2. Can you write the key signatures for any given majore key?
3. Can you remember how many sharps or flats each of the major key has?