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):


Questions that you should be able to answer by the end of this lesson:
- Can you name the associated major key by looking at the key signatures?
- Can you write the key signatures for any given majore key?
- Can you remember how many sharps or flats each of the major key has?