Flats order

The order of flats is:

B♭ E♭ A♭ D♭ G♭ C♭ F♭

But you can remain only:

B E A D G C F

How to memorize the order of flats

The trick is to memorize the word BEAD plus three letters GCF.

Another trick to memorize the orders of flats: Battle Ends And Down Goes Charles Father

Why to learn by rote the order of flats?

With the order of flats always in mind you will be able to do:

- Knowing all Altered notes in your music score (music notes with accidentals, flats in this case)
- Finding the name of the key signature.

Knowing all Altered notes

Imagine you have 4 flats in the key:



With the order of flats in mind, you immediately know the altered notes you will find in the score: B♭ E♭ A♭ D♭ G♭ C♭ F♭ and you will know that the previous score below is just like this:

Finding the name of the key signature

With the flats order, you can find the name of the key signature:

Imagine you have this (4 flats in the key)



With the order of flats, you have this: B♭ E♭ A♭ D♭

You find the second to last flat in this sequence: B♭ E♭ A♭ D♭, here it is A♭, so you know that the name of the key signature is A♭ Major.

External links to learn more about :

1 - https://www.dolmetsch.com/musictheory9.htm
2 - https://en.wikipedia.org/wiki/Accidental_(music)
3 - https://musicterms.artopium.com/a/Accidentals.htm