8.21 Applying the circle of fifths

In Chapter 8.20 The circle of fifths you’ve learned what the circle of fifths is. In this chapter, you will learn how to apply the circle of fifths.

1. What can you do with the circle of fifths?

Using the circle of fifths, you can:

1. calculate the number of sharps or flats in a scale.
2. determine the scale, if you know the number of sharps or flats.
3. determine the key of a piece of music.

Five examples of these methods:

2. Determing the scale: which major scale has four sharps?

The half of the circle of fifths with sharps gives us the scale of E major: C (0) - G (1#) - D (2#) - A (3#) - E (4#).

Examples

3. Determing the scale: which major scale has three flats?

The half of the circle of fifths with flats gives us the scale of E flat major: C (0) - F (1b) - Bb (2b) - Eb (3b).

Examples

4. Determing the scale: which minor scale has two flats?

The half of the circle of fifths with flats gives us the scale of B flat major: C (0) - F (1b) - Bb (2b).

A minor third below Bb is G: the G minor scale has two flats.

Examples

5. Determing the accidentals: how many accidentals does the scale of A major have?

The half of the circle of fifths with sharps gives us three sharps: C (0) - G (1#) - D (2#) - A (3#).

Examples

6. Determing the accidentals: how many accidentals does the scale of F major have?

The half of the circle of fifths with flats gives us one flat: C (0) - F (1b).

Examples

7. Determining the key: what is the key of a piece of music?

We can recognize the key of a piece of music by two steps:

1. counting the number of accidentals in the scale.
2. looking at the last measure and its final pitches or chord to determine the tonic, which is the tone of the key.

The tonic of the final chord is also the tonic of the scale in which the piece was written, the final chord is almost always the first degree.

Examples

The bass tone, or lowest tone of the final chord is almost always the tonic.

Look closely to find the final measure, this is not always the last notated measure (for example, when a piece ends with D.C. al Fine).

8. Practise

Harmony exercise 8w: practise applying the circle of fifths.

Using the circle of fifths, you can:

1. calculate the number of sharps or flats in a scale.
2. determine the scale, if you know the number of sharps or flats.
3. determine the key of a piece of music.

Harmony exercise 8w: practise applying the circle of fifths.