Mr Cato's Key Signature Trick

Music Theory Major Scale Theory & Key Signatures
47

Hello @PJPro and welcome to the community.

For awkward keys, which you can figure out on paper but which you will likely not use in practice, there are several approaches.

D# is a key one semitone above D.
List the D major scale:

D major scale → D, E, F#, G, A, B, C#

Rewrite it with all notes raised by a semitone - but, crucially, maintaining the alphabetical list exactly the same.

D# major scale → D#, E#, F##, G#, A#, B#, C##

That is quite ugly isn’t it? Yet it exists in music.

You could do the same going in the opposite (flat) direction.

D major scale → D, E, F#, G, A, B, C#

Db major scale → Db, Eb, F, Gb, Ab, Bb, C

All notes lowered by one semitone.

Alternatively, you could use the circle of fifths which has all keys in all directions both sharp and flat. The Circle of Fifths Part 1 - where does it come from?

I hope that helps.

Cheers :smiley:

| Richard_close2u | JustinGuitar Official Guide, Approved Teacher & Moderator

48

Just got to this lesson on the course but slightly confused. I can work out how to get the number of b’s and #'s in a key but not how then to get all the rest of the notes. See the example below:

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So we know that there are 2#'s in the key of D but it’s a big jump to then know the rest of the notes, or is this just a case of using the Major Scales worksheet from the earlier lesson? At this stage there is no way that I can remember all notes in each key.

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49

Hi Stuart,

I usually use the major scale formula (TTSTTTS, see the lesson and the worksheet) plus a few hints, like:

  • Degree VII is always a semitone lower than the root note (e.g. C# in D major)
  • “New” sharps appear on degree VII
  • Degrees III and V are in the major chord formula as well (e.g. D - F# - A)

As for the order in which sharps and flats appear, I’d suggest to check out @Richard_close2u’s extra material on the circle of fifths as it’s really well-written and informative, starting with all the basics you need to know. So, in time, you’ll be able to tell things like which major scales may have an A# in them.

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50

@Stuartw it’s easy. Every major scale has 7 notes A B C D E F G.
Using Mr Cato’s chart you know in the key of D major the C and F are sharp. So starting with the root D the note of the D major scale are D E F# G A B C# D.
Using Mr Cato’s chart write out the notes of the A major scale.

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51

It is now!! Went back and had another look at this and it’s a whole lot clearer.

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52

Hi first post so please don’t shoot me down, I find playing the chords in order with C being 0, G being 1, D being 2 , A being 3 etc , really helped me visualise this. I know F is that start point and then I just add in the letter of the chord sharps I’ve already played. The visualisation on the keyboard cracked this in a couple of days for me. Trickier with the flats but play in reverse and add in the next chord. (ignoring the F, as F is always a problem! ) , I hope that helps someone.

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53

Im lucky enough to have a wife who has over 20 years of classical piano training. i’ve been learning guitar from you over the last year and now these fascinating theory classes have sparked some funny memories for my wife when she was a little girl.
When she was 7 years old her piano teacher told her and her classmates to come up with their own mnemonics to remember the order of the sharps.
Long story short. Her older classmates all came up with some fancy sentences for the FCGDAEB layout. When it was her turn to say how she remembered she just blurted out…
“FUH, CUH, GUH, DUH, AH, EE, BUH!”
Her classical piano teacher couldn’t hold it together and just burst out laughing.
Now my wife and I share this strange alien language with each other when we randomly blurt out, FUH, CUH, GUH, DUH, AH, EE, BUH!"
I’m loving all of your classes, thanks for putting all this together Justin!

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55

It’s that last step that usually gives people brain-strain! I used to find it difficult as well, but you’ll be amazed at how quickly you will internalise the most commonly-used keys, and will know that, for example, D has two sharps - F# and C# - or that Ab has four flats (Bb, Eb, Ab and Db). You won’t have to work it out; you’ll just know.

Yep. That is simply slick as a whistle. And it works! Even my elderly brain can wrap itself around that concept. Way cool. I guess my next couple of practice sessions will be internalizing Mr. Cato’s diagram.

Finicky Chicks Get Darn Annoyed Eating Baloney

Thanks!

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57

This is an amazing lesson! Been working on memorizing this and i stumbled on an interesting observation that i think i’m going to use to remember this. I observed that if i memorize just the right side of Mr. Cato’s diagram i can work out the equivalent flat and sharp key signatures. E.g. Memorize the A major using Mr. Cato’s diagram.
A maj = A, B, C#, D, E, F#, G#
A# maj = Replace all sharps in A maj with natural and replace all naturals with sharps = A#, B#, C, D#, E#, F, G
Ab maj = Replace all sharps in A maj with natural and replace all naturals with flats = Ab, Bb, C, Db, Eb, F,G
Only 2 exceptions to this trick
F# maj = The Bb in F maj becomes B natural in F# maj
Fb maj = The Bb in F major becomes a Bbb double flat in Fb maj
It was one of those amazing light bulb moments when i stumbled on this :- )

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58

Lots of good replies. I think with such a heady topic, everyone is going to have different things that clicks. I had a good mnemonic device, but this works better and is more instantly obtainable by my brain because it matches up with the power chord root notes I’ve already memorized without having another mnemonic to remember. Seeing the letters separated like in your image (as if it’s the 6th and 5th strings) made this click for me. Thank you.

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59

So, I have a mnemonic, I have Mr. Cato’s diagram memorized and I can mostly go through the diagram in my head to name the notes of each key. I can definitely do it if I draw out the diagram. Since this is the only part about module 3 that I’m still working on, I’m wondering if it’s a good time to move to module 4 or should I be able to name the notes in each key straight away without thinking about or drawing a diagram? I want to make sure my foundation is solid but also want to make sure I’m not treading water here longer than I should.

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60

About F# and C#: Mr Catos method works for these too, however we have to consider their respective enharmonic equivalents. For F# we have Gb. So, we can write Gb scale using Cato and then write the equivalents for flat notes. We end up with B as the only natural note, which is consistent with the major scale table and Formula.

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61

Waittttt, ive got a brainfart. Why is the scale of C# different from a Db? In my head C# is the same thing as a Db…!!!

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62

Hey Brian,

Welcome to the community mate !

Re your brainfart - which are always good;

C# Major Scale

C# d# e# f# g# a# b#

Db Major Scale

Db Eb F Gb Ab Bb C

See how different they really are.
In this example, which one would you see as more logical, and much easier to use?
The C# scale has a b#, and an e#; really just theoretical. In fact all are sharps here. Not really cool in my opinion. Messy.

Also the notes eg. Db and C# ( and any enharmonic equivalents like these), will have different functions in the same key.
Ie. They are different intervals from the root note.

Eg.
In A major
C# is the major 3rd
Db is the diminished 4th.

Same pitch, yes. But different qualities, different functions.

Cheers, Shane

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63

Ahh, got it!

Cheers mate

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64

So I’m looking at the Cato Keys Diagram on JG-PMT-Grade3-Workbook. It says the key of C has no sharps or flats, but then in the diagram is showing C has 7 flats. I’m sure I’m not understanding it the right way. Looking for a more in-depth explanation of the Cato keys concept.

catokeys
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65

Welcome to the forum Adam
Cato Key Diagram is another way of look at the circle of 5th. The letter represent how the sharps and flats appear in each key. The key C has 0. The key of G has 1 sharp. The key of D has 2 sharps etc. Going to the left is how the flats appear. C has 0. F has 1 flat. Bb has 2 flat etc

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66

Hi Adam, welcome to the community! It took me a bit to get my head around this diagram (I’m still a music theory novice). The way to read it, though, is that key of C has no sharps or flats, but the key of C flat has 7 flats.
If you have a minute, consider introducing yourself over here. :blush:

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67

Hi there,

Personally, I never really got the hang of this diagram so I rely on other prompts.

An easy comparison to start with:

  • C major: no accidentals (sharps/flats), only natural notes
  • Cb major: 7 flats (all notes are flattened compared to C major)
  • C# major: 7 sharps (all notes are sharpened compared to C major)

Order of appearance of sharps: see circle of fifths (C - 0, G - 1, D - 2, etc.) - the names of the open strings will help.
Order of appearance of flats: see circle of fourths which is the anticlockwise direction on the circle of fifths (C - 0, F - 1, Bb - 2, etc.) - the names of the open strings again will help.

Another useful notion about the number of accidentals following from the C/Cb/C# major comparison:

  • 5 sharps in B major & 2 flats in Bb major: 5+2 = 7
  • 3 sharps in A major & 4 flats in Ab major: 3+4 = 7

And so on.

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68

Incidentally, East Brighton is home to a wonderful football club, Whitehawk FC. Fans Can Get Drunk At East Brighton.

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