[MUSIC] In the last lecture, you learned that we use key signatures to reduce the need for accidentals. When a piece is in E flat major, we can use a key signature of B flat, E flat, and A flat. So that whenever a note falls on the B, E or A lines or spaces we will automatically flat it. The slow way of figuring out key signatures is to figure out the major scale using the interval pattern of two whole steps, half step, three whole steps, half step. So D major would be D, E, F-sharp, G, A, B, C sharp and D. In this lecture, I'm going to show you how to figure out the key signature a faster way. Remember to memorize the order of the sharps and flats. Just recite it to yourself enough times that you know it cold. F, C, G, D, A, E, B for sharps, and B, E, A, D, G, C, F for flats. You must know this when figuring out key signatures quickly. If I ask you to write the key signature for B major, not B flat major by the way, you can do it the slow way by figuring out the notes of the scale using whole steps and half steps then counting up the sharps. The notes are B, C sharp D sharp, E, F sharp, G sharp, and A sharp. So there are five sharps, F, C, G, D, and A, when we put them in key signature order. But there's a shortcut, a version of which many musicians use. The last note of the scale, T, or the half step below the tonic is always the last sharp in the key signature. For B major, that note is A sharp. If you know the order of sharps, you just zip through them until you get to that sharp. F, C, G, D, A, then you put them in the correct order on the staff, and then you have the key signature. Here's another one, A major. A half step below A is G sharp, using the previous letter name of course, we can't call it A flat. So F, C and G are the sharps, here they're on the grand staff. Remember, you must put the key signature on both staves when you have a grand staff. It's very important that you always think sharps and flats when looking at a sharped or flatted note. Students sometimes get sloppy and think A major when they're looking for A flat major, or F major when they are looking for F sharp major. They are very different keys. What is the key signature of D major? The last note of the D major scale is C sharp, so the sharps are F and C. What is the key signature to F sharp major? A half step below Fsharp is either F, which we can't use, or respelled, it's E sharp. So the sharps are F, C, G, D, A and E. Why can't we call the note F? Because we can only use every letter only once in a diatonic scale. No diatonic scale will have an F and an F# in it. When we do minor scales, we will occasionally need to use double sharps for the same reason. Figuring out the major scale from the key signature is the same process, only backwards. What is the major key with four sharps? The sharps are F, C, G, and D sharp. The last sharp, D sharp, is the last note of the scale, a half step below the tonic, which will be E, so E major. You do one now, what major key is this? The sharps are F, C, G, D, A and B sharp. B sharp is the same as C natural, but we can't call it that, because then we wouldn't have any Bs in our scale. So B sharp is a half step below C sharp, which is the tonic. C sharp major then has seven sharps, notice that every note is sharp in C sharp major. That's it for sharps, remember the last sharp has a half-step below the tonic note which must have a different other name. In the next lecture we'll do flats, which are a little trickier but still pretty easy. But remember, the fastest way to figure out key signatures is just to know them. Five sharps, B major, two sharps, D major and so on. [MUSIC]
