Welcome to LivingPianos.com, I’m Robert Estrin. Today I’m going to share with you the magic formula for key signatures. Many of you know your key signatures. But maybe you don’t quite understand them or you’re not fluent with them. Do you need to memorize all that stuff? Surprisingly the answer is no. Why not? There are formulas you can use to figure them out!
You never have to memorize your key signatures.
Believe it or not, I have never memorized my key signatures, but I can name them. F, C, G, D, A, E, B. How did I do that so fast? I’m actually thinking through the intervals that fast. I’m going to show you how to do exactly the same thing so that you don’t have to memorize them. You can understand them and figure them out. You might not be able to figure them out as quickly as I just did, but you will be able to figure them out. You will get faster with it over time.
The interval of a fifth is critical in key signatures.
What is a fifth? The fifth, simply put, is the fifth note of a scale. So in C major, G is the fifth note of the scale. This interval is what’s called a perfect fifth. It’s a perfect fifth because G is the fifth note of the C major scale. You can invert this and put the C on top. It’s still a perfect interval, but now it becomes a fourth. So fourths and fifths are essentially the same. That’s one of the reasons they’re perfect intervals. Inverted, they remain perfect. Incidentally, octaves are also perfect intervals, as well as primes or unisons. If two people are playing the same note on different instruments, that’s called a prime. Once you understand fifths and fourths, the rest is easy!
If you have a key signature with sharps, the first sharp is always F-sharp.
You have to memorize that F-sharp is the first sharp. Once you memorize that and a couple other small details, the rest is seamless. So you have F-sharp. From there it goes up by fifths. You can either count with your fingers or you can do it on the piano. Count out five notes, F, G, A, B, C. C is the second sharp. From here you count out the next one, C, D, E, F, G. G is the next sharp. You can keep counting this way. D is the next sharp, then A, then E, and the last sharp is B. So these are all the sharps, F, C, G, D, A, E, B. You don’t have to memorize them. You just have to be able to figure them out.
How do you know what key you’re in?
If you go up a half step from the last sharp to the right, that’s the major key. So if you have one sharp, an F-sharp, go up a half step to see you’re in the key of G major. If you have two sharps, F-sharp and C-sharp, you’re in the key of D major. If you have three sharps, F-sharp, C-sharp, G-sharp, you’re in the key of A major. If you have four sharps, F-sharp, C-sharp, G-sharp, D-sharp, you’re in E major. If you have five sharps, F-sharp, C-sharp, G-sharp, D-sharp, A-sharp, you’re in B major. With six sharps you end on E-sharp, which means you’re in the key of F-sharp major. And finally, all seven sharps mean you’re in the key of C-sharp major.
That’s just half the story, because now we go to flats!
The first flat, if you only have one, is going to be B-flat. From here it goes down by fifths. I mentioned earlier that fifths and fourths are the same thing reversed. So you might as well go up by fourths because it’s easier to count up than down. So B-flat, E flat, A-flat, D-flat, G-flat, C-flat, F-flat. That’s the order of the flats. This is exactly backwards from the order of the sharps. The patterns are unbelievable!
Finding what key you’re in is even easier with flats.
There is one that you must memorize. The key with one flat is F major. It has the B-flat in it. You just have to know that. From there, the second to last flat is the key you are in. Because all flat scales, with the exception of F major, begin on a flat. So if you have two flats, B-flat and E-flat, you’re in the key of B-flat major. If you have three flats, B-flat, E-flat, A-flat, you’re in the key of E-flat major. If you have four flats, B-flat, E-flat, A-flat, D-flat, you’re in the key of A-flat major. And it goes on and on that way.
So all you have to look for is the last sharp on the right and go up a half step to find your major key. Or look for the second to last flat to the right to find the major key. I hope you enjoy these theory primers! Let me know in the comments here at LivingPianos.com and on YouTube. Thanks again for joining me, Robert Estrin here at LivingPianos.com, Your Online Piano Resource.
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6 thoughts on “The Magic Formula for Key Signatures”
Great thanks
The perfect fith interval up for sharps and coming down will be the flat s circle of fith’s. Opposites of each other but very cleverly organised for children to grasp.
It is always fascinating how to start with the f sharp .To say that it is the only sharp to remember makes sense and the rest follow suit.I must have a starting point.
I also teach the falts with counting a fourth , a perfect , up and that belongs to F major. The second to last flat is the new flat scale is a very easy way to remember as well.
Looking forward to the minor video.
Here are 2 videos on relative minors: https://livingpianos.com/what-is-a-relative-minor-scale-music-theory-lessons/
and https://livingpianos.com/how-to-tell-if-a-piece-is-in-a-major-or-minor-key/
Very helpful summary. I’m prepping to teach basic theory to some child relatives who take piano, so it’s good to see how others would explain it. One question I’m mulling is whether to do it all without the keyboard. I think that’s more traditional.
I get students to do it both ways – using the keyboard, and counting on their fingers.
I’m confused. If the 5th note of the C scale is a G, isn’t the 4th note an F. But you’re making it sound like G is a perfect 5th going up and a perfect 4th going down the C major scale.
I thought that F was a perfect 4th in the scale regardless of direction.
If you count up to the 5th notes of the C major scale, you reach G. If you count down 4 notes in a C major scale, you also reach G.
5ths and 4ths are the same intervals when inverted.
So, if you count up to the 4th note of a C major scale you will reach F. If you count down 5 notes in a C major scale you will also reach F.