Why Learn the Circle of 4ths?
Have you read my article on the Circle of 5ths? I’d recommend starting there. If you’re still with me, the Circle of 4ths and the Circle of 5ths are two sides of the same coin. 4ths help you with flats (b), 5ths help you with sharps (#).
Once more, please. Why is this stuff important?!
You can play basic harmonica just fine without this info, but wouldn’t it be cool to know exactly what notes are available in every major key? Might it not be helpful sometimes to know exactly which notes your harmonicas are tuned to, on every hole?
What’s a 4th?
An interval: the distance between two notes. If C is note 1, then counting alphabetically, F is note 4.
C D E F 1 2 3 4
F is a fourth above C.
Natural Notes, Sharps (#) and Flats (b)
There are seven natural notes: C D E F G A B
There are five sharp / flat notes:
F#/Gb
C#/Db
G#/Ab
D#/Eb
A#/Bb
The notes with sharps and flats each have two names. They can be named as a lower note name with a sharp, or as a higher note name with a flat.
We’re going to focus on flats in this article.
Examples of Flat Keys
The key of C has no sharps or flats.
C D E F G A B C
The key of F has 1 flat: Bb
F G A Bb C D E F
The key of Bb has 2 flats: Bb, Eb
Bb C D Eb F G A Bb
The key of Eb has 3 flats: Bb, Eb, Ab
Eb F G Ab Bb C D Eb
The key of Ab has 4 flats: Bb, Eb, Ab, Db
Ab Bb C Db Eb F G Ab
What’s the Pattern?
Key Names
Let’s start with the key names: C F Bb Eb Ab
From C to F is a fourth.
From F to Bb is a fourth.
From Bb to Eb is a fourth.
From Eb to Ab is a fourth.
The flat keys are following the Circle of Fourths!
Flats
Now let’s look at which notes have flats: Bb, Eb, Ab, Db
From Bb to Eb is a fourth.
From Eb to Ab is a fourth.
From Ab to Db is a fourth.
The flat notes are also following the Circle of Fourths!
Conclusion: Flats
1. To learn the flat keys, start with C and follow the Circle of 4ths.
2. Each new key will add one more flat to the previous one’s key signature.
3. To learn which notes are flat, start with Bb and follow the Circle of 4ths.
Like to Memorize Stuff?
Circle of 4ths
C F A#/Bb D#/Eb G#/Ab C#/Db F#/Gb B E A D G C
Flat Notes
Bb Eb Ab Db Gb
Scales with Flats
C D E F G A B C F G A Bb C D E F Bb C D Eb F G A Bb Eb F G Ab Bb C D Eb Ab Bb C Db Eb F G Ab Db Eb F Gb Ab Bb C Db