How Key Signatures Work
This guitar lesson will teach you how to find out the key signature of a given key and how to tell what the sharps or flats in that key are. It is probably best to just memorize your key signatures, but understanding this how key signatures work will go a long way in helping you to be a better musician. First we will look at the sharp keys and then we will move on to flat keys.
There are two sequences of notes, one for sharp keys and one for flat keys, that you can use in order to figure the key signature and number of sharps or flats for any given major key. For sharp keys the sequence is FCGDAEB and for flat keys the sequence is BEADGCF. The sequence FCGDAEB can be remembered by the phrase ”Father Charles Goes Down And Ends Battles”. That may seem a bit silly but it will help you to remember the names of those notes in the sequence. You can also think of what we call the cycle of 5ths in order to remember this series of notes. Start on the F and count up 5 notes to a C. Now count five notes from C to a G. If you keep counting up five notes every time you end up with FCGDAEB.
Since the key of C major has no sharps or flats we will use it as the starting point in the sequence. Look at the G note in the sequence. It is the next letter right after C. The key of G major will have one sharp. You could also say that the key signature for G is one sharp. Now look at the next letter in the sequence, it is a D. The key of D major will have two sharps. Continue down the sequence with this same idea and you will find that the key of A major has three sharps, E major has four sharps and so on.
Now we need to find out which sharps go with the key signatures we just found. Take the key of D major for an example. We found out that the key signature for D major is two sharps. Go back to the very beginning of the sequence FCGDAEB. The first letter is an F and the second is a C. Those are the two sharps in the key of D. Take this one step further with the key of A major. A major is the third note away from C in the sequence so the key signature would be three sharps. Those three sharps are F sharp, C sharp, and G sharp.
The sequence of notes for flat keys is BEADGCF. You can think of the word “BEAD” to remember the first four notes and “juicy fruit” to remember G C and F. I know juicy is spelled with a j not a g but it helps to remember the sequence. Look carefully at this sequence. BEADGCF is just FCGDAEB backwards. Instead of a cycle of 5ths, BEADGCF is a cycle of 4ths. Four notes away from B is E, four notes away from E is A and so on.
The sequence for flats works the exact way that the sequence for sharps does. Start on the C. Remember the key of C has no sharps and no flats. The next note over in the sequence is an F. The key of F major has one flat in it. Go all the way back to the beginning of the sequence to the B. That is the one flat in the key of F major. Start on the C again and go two notes over. F would be one and then you would go back to the beginning of the sequence to a B for the second note. This would be the key of B flat. Since B flat is two notes away from C in the sequence it will have two flats. Those two flats are B flat and E flat.
This is a lot of information to absorb in one lesson so don’t feel bad if you did not catch everything the first time through. Try to find out the key signatures for other major keys using the two sequences. Once you think you have the answer look it up on the Internet to see if you are right. Of course the best thing to do is just flat out memorize all of your key signatures.