Music Video Lesson: The Magic Formula for Key Signatures

F sharp, C sharp, G sharp, D sharp, A sharp, E sharp, B sharp.

You're in the key of, you guessed it, C sharp major.

Welcome to livingpianos.com. I'm Robert Estrin with the magic formula for key signatures. Now many of you know your key signatures, but maybe you don't quite understand them or you're not fluent with them. You wonder, do you need to memorize all that stuff? And the answer is no, surprisingly. Why not? Because there are formulas where you can figure them out and you never have to memorize them. Believe it or not, I have never memorized my key signatures. ["Gasps"] But I can name them F, C, G, D, A, E, B. How did I do that so fast? Because I'm actually thinking the intervals that fast. I'm gonna 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 and you will get faster with it over time. All right.

The interval of a fifth is critical in key signatures. What is a fifth? Well, the fifth, simply put, is the fifth note of a scale. So in C major, C is one, two, three, four, five. So that's what's called a perfect fifth. It's a perfect fifth because G is the fifth note of the C major scale. Now you can invert this and put the C on top. It's still a perfect interval, but now it becomes a fourth. One, two, three, four.

So fourths and fifths are essentially the same. That's one of the reasons that they're perfect intervals. Inverted, they remain perfect. Incidentally, octaves are also perfect intervals as are primes or unisons.

If two people are playing the same note on different instruments, that's called a prime. A perfect prime is the same note on two instruments. Octave, fifths, and fourths, or fourths. Now, once you understand fifths and fourths, the rest is easy. Let's start with it. You do have to know just a couple of little things. You notice that if you have a key signature with sharps, the first sharp is always F sharp. You do have to memorize that. Once you memorize that and a couple of other very tiny details, the rest is seamless. Now, you have F sharp. And from here, it goes up by fifths. You can either count with your fingers F, G, A, B, C, which is a second sharp, or you can do it on the piano. F, G, A, B, C. C is the second sharp. From here, you go to the next one, C, D, E, F, G. G is the next sharp. G, A, B, C, D is the next one. D, E, F, G, A is the next one. A, B, C, D, E. And the last sharp is E, 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. F, G, A, B, C, C, D, E, F, G, G, A, B, C, D, D, E, F, G, A, A, B, C, D, E, E, F, G, A, B. Or you can do it on the piano.

That's the sharps. Now there's a simple formula. You might wonder, how do you know what key you're in? Well, if you go up a half step from the last sharp to the right, that's your major key. So if you have one sharp and F sharp, go up a half step, you're in the key of G. If you have two sharps, F sharp and C sharp, you're in the key of D major. 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, E sharp, yes, E sharp, you're in the key of F sharp major. And finally, all seven sharps, F sharp, C sharp, G sharp, D sharp, A sharp, E sharp, B sharp, you're in the key of, you guessed it, C sharp major.

This makes perfect sense when you consider that seven sharps, and to C major has no sharps or flats, you go to seven sharps and they're all sharp because there's seven different notes. So really, you could start on C, I started on G, but start on C, go to the fifth note, G, G major has one sharp, D major has two sharps. Once again, going five notes, the fifth note of the D major scale goes to A major with three sharps, fifth note of the A major scales, E with four sharps, et cetera, et cetera. And 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, but 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, B flat, E flat, A flat, D flat, G flat, C flat, F flat.

That's the order of the flats. Some of you may have caught on that this is exactly backwards from the order of the sharps. F sharp, C sharp, the flats backwards.

So the sharps are F, C, G, D, A, E, B, and the flats are backwards from that. B, E, A, D, G, C, F, or B up fourths, E, A, D, G, C, F. The patterns are unbelievable. They're all over the place. Now, I had that little trick for you to figure out what key you're in with sharps. Just go up a half step from the last sharp on the right. It's even easier with flats. There is one you must memorize. The scale with the key with one flat is F major. It's got the B flat in it. You just have to know that. From then on, the second to last flat is the key you are in because all flat scales with the exception of F major all begin on a flat. So if you add 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, and A flat, you're in the key of E flat major, the second to last flat. If you're in 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. Go up a half step. That's your major key. The last flat, second to last flat to the right, that's your major key. Now there is something called relative minors, which is the subject for another video for you. I hope you enjoy these theory primers. Let me know in the comments here at livingpianos.com and YouTube. And thanks for joining me here at livingpianos.com, your online piano resource with a whole lot more coming your way. Thanks for subscribing, ringing the bell, and those thumbs up if you enjoyed the videos. I'm Robert Estrin, seeing you next time.

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