Mr Cato's Key Signature Trick

Here's a brilliant and simple trick to help you remember the notes of each Major Scale.

View the full lesson at Mr Cato's Key Signature Trick | JustinGuitar

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I came up with a very small trick as I was writing out the notes in the major scales to help quickly find out how many sharps and flats are in each key. It doesn’t work for every key, but if you look at how many lines it takes to write the the letter (in caps) of the key you are looking at it will sometimes reveal how many sharps/flats.

Ex.) It takes 3 lines to make the letter "A ", 4 lines to make the letter “E”, 2 to make a “D” , & if you make the curves on your “B” triangles it will take 5 lines… The number of lines tells you how many sharps/flats are in the key. It may only work for these keys and if it is too confusing then you should ignore it, but it helped me memorize A - G a lot more quickly!

I hope it can be helpful for someone else too!

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I use this a great deal, it makes perfect sense. What a great visual. Thankyou Justin for passing it on, and thankyou Mr Cato.

Hope this makes sense for F# and C#:

I think of the sharp side of the diagram repeating after reaching B. So we got to B and have 5 sharps. Now the diagram ends and repeats from the double line in the middle with 5 sharps in our bag. F# is the first scale and will have 6 sharps, C# follows immediately after and has 7 sharps. Helps that in my mind the double line in the middle looks like the notation for a repeating section in tabulature.


Hi, New to the theory course.
I loved Mr Cato’s diagram to find out how many #'s and b’s are in each key. I can see it caters for ‘natural’ keys to the right and ‘flats’ to the left, but I cant see where it caters for any of the Sharp Keys A# C# D# etc? Apologies I’m obviously missing something!

Love this course and key signature trick but you should probably at least mention this tool doesn’t encompass sharp scales, only flats and naturals. Or even a short summary why it won’t work and an alternative.

I just wanted to clarify, we write FCGDAEB, but the reason we write that doesn’t have to the F# C# G# etc. that we write on a music stave, right? Sorry if that’s confusing. I’m just trying to understand if there’s any connection between Mr. Cato’s FCGDAEB and the FCGDAEB (sharped) that we write on a music stave

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I clipped this from Justin’s lesson. Let’s see if I can explain it to you @hakolsababa. I learned this years ago in piano lessons, and the mnemonic I learned was Father Christmas Gave David An Empty Box. Whatever mnemonic you use, the order of sharps is the first letter of the mnemonic: FCGDAEB. Starting at the C, the key of C has zero sharps, G has 1, D has 2, etc. So for E, which has 4 sharps, the sharps are FCGD. So yes, there is a relationship. (Note that after you get to B with 5 sharps, you have F# with 6 sharps, and C# with 7 sharps. Realistically those would very rarely be used, C# in particular because it’s enharmonically the same as Db, and (at least in piano) that’s an easier key (5 flats instead of 7 sharps).

To finish the rest of the explanation, going backwards, from F, so FBEADGCF, although adding a flat to each key starting at B, that is the order of keys according to number of flats: F has 1 flat, Bb has 2, Eb has 3, etc. The actual order of flats in the key signature is BEADGCF. Based on this Db would have 5 flats, and they would be BEADG.

It’s rather a perfect little tool for remembering key signatures, and order of flats and sharps.

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Hi there @Earthless . If you keep going past the B which has 5 sharps you would go to F# with 6 sharps, and then C# with 7 sharps (so go to the beginning of the cycle, and add a #). As per my reply above realistically F# and C# would very rarely be used, but they do fit the pattern if you extend the cyclical pattern out a bit ( and add the #s, same as you have to add the flats when you figure out the keys with flats).

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You can also use the fretboard to figure this out. The order of sharps are the circle of 5th and flats circle of 4ths. If the 1st and 2nd guitar strings are barred on the first fret (EADGCF), all of the strings are a 4th apart going from lower to higher and a 5th apart going from higher to lower. The only note missing is B which can be added above the F (EADGCF-B)

To find the number of flats or sharps for a key just count strings in the correct direction until you reach C. Works for finding which notes are sharp and flat as well in a key as well. Order of flats BEAD… Order of sharps FCG…(just go backward from the -).

My gods after months of trying I think I’ve finally got it. It takes ages of counting on my fingers but I can finally work out a key on a stave.

I would definitely need a sheet in front of me to work out the notes in a scale but that is alowed it seems lol

Thanks for the lesson Justin! What a great diagram this is. A really easy way to remember.
To add a little something, here’s a little tip about sharps and flats from Victor Wooten.
Easy way to remember this is to see a flat key and a sharp key (with the same note in the name) as sort of opposites, and that amount of accidentals in both of those adds up to 7. Whichever notes are accidental in one key will be natural in its ‘opposite’ key (not sure how those would be called in correct musical terms).
Here’s what I mean - let’s say, you picked a key of B major. It has 5 sharps. Now, if you wanted to find out how many flats Bb major has, you would do 7-5=2 flats.
Accidentals in Bb major would be notes that are natural in the key of B major, and vice versa.
Same goes for everything else with the exception of F - F major is a flat key with 1 accidental, so to flip this one you’d have to go to F# major (instead of Fb major), and it would have 6 (still adds up to 7).
Just a nice little addition that could be of use to somebody.
Thanks again!


All good stuff @wobba_bobba Music & Maths - it all adds up! :wink:

Brilliant, and presented in a straight forward manner.I really like how this material is being presented. Thank you Mr. Cato, Justin and those who added some interesting, and helpful, comments!

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Hello @Papa_G and welcome to the Community.
Glad you’re digging the lessons and learning.

Cheers :smiley:
| Richard_close2u | JustinGuitar Official Guide

Here’s my rhyme for remembering “F C G D A E B”. Think Monte Python and the Holy Grail. “French Castle Guidance, Dads Are Elder Berries” Might be a rhyme that will be more universally applicable than Justins. :wink:

Maybe someone already made these few observations but if not, here they are:

1- In order to write down the diagram, you only need to remember FC because the other letters follow a similar pattern, i.e., G and D are the letters that follow F and C, and A and E follow G and D, and finally, B follows A:

F       G        A       B
    C        D        E

2- For F# and C#, if you extend the diagram to the right, I believe the system still works:

Fb Cb Gb Db Ab Eb Bb // F C G D A E B F# C#

B has 5#, F# has 6 and C# has 7.

I hope this helps! (I also hope I didn’t mess up :P)

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Spot on! Love it!

A useful mnemonic I learnt from my kids piano teacher is “Father Charles Goes Down And Ends Battle” for the order in which sharps appear, and “Battle Ends And Down Goes Charles Father”, for the order in which the flats appear. A sentence that (sort of) makes sense forwards and backwards…. Hope this helps others.

This only applies to the major scale correct?

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