Key Signatures Explained

A brief explanation of key signatures.

Ultimate Guitar
Although this topic has most likely been covered by other users, I decided to write about it myself ---because of a couple of comments I received after an article called Awkward Key Signatures Made Easy'. It was clear from the comments, that the people who didn't understand the point of the article, were a little confused about key signatures in general. Believing that they have more to do with pitch and fingerings than note names. It was this false assumption that was at the heart of the misunderstanding. So I thought I'd go into a little more detail about what a key signature is, which key signatures are most commonly used and why. What Is A Key Signature A key signature is nothing more than the marks made at the start of a piece of music - or before a key change - that tell the musician which key the music is in. For example, in the key of G, a sharp sign would be written on the F line. It tells the musician that, unless otherwise indicated, all F's are to be played sharp. This saves the composer having to write a # sign before every F on the score. How To Write A Key Signature Correctly A key contains seven notes. When writing the key signature, each of these seven scale degrees must have it's own line on the staff. That is to say, each note has it's own letter name, I.e, A, B, C, D, E, F and G. And each of these must be given a value of either flat (b), sharp (#), or natural (the line is left blank). This means that you can't have two notes with the same name in one key signature. For instance A and A#, or Bb and B. The reason for this becomes obvious when you consider how one goes about leaving a line blank and writing a sharp or flat sign on it as well. This rule can introduce some confusing note names such as: Cb and E#. The Twelve Most Commonly Used Key Signatures There'll be some amongst you (of the type I encountered after my last article) who'll be dying to point out that The Twelve Most Commonly Used Key Signatures' is a bit of an oxymoron. But wo there horsey. Theoretically, the number of key signatures is infinite. Remember that they're just names for things. Just as Bb and A# are 2 different names for the same thing. When dealing with key signatures, It's better not to think in terms of pitch and fingerings. Again, I'd like to emphasise that this is about written music and not the fret or keyboard patterns. So why is it preferable to mark the key as Ab rather than G#? Well, let's use the circle of fifths to work our way through and find out.
KEYNo. of sharps
G1 (F)
D2 (F, C)
A3 (F, C, G)
E4 (F, C, G, D)
B5 (F, C, G, D, A)
F#6 (F, C, G, D, A, E)
At this point I'm going to substitute F# for Gb and continue moving up in fifths.
KEYNo of  flats
Gb6 (B, E, A, D, G, C)
Db5 (B, E, A, D, G)
Ab4 (B, E, A, D)
Eb3 (B, E, A)
Bb2 (B, E)
F1 (B)
So we began with C containing no sharps, and we moved through the key signatures in such a way as to arrive back at C, which also contains no flats. A perfect circle. And isn't it a beautiful thing? Look at the symmetry. Not only do we move up in fifths to discover that the next key contains one more sharp, but we also move up in fifths to find out which sharp it is. F up to C, up to G etc. Adversely, if we start at C containing no flats and move DOWN in fifths, not only do we discover that the next key contains one more flat, but by moving down in fifths we also discover which flat it is. B down to E, Down to A etc. Wonderful! So now we can see why we write in Bb and not A#. If, instead of substituting F# for Gb, we were to continue on with the first table, we'd find that C# was the next key. And using the formula established by the previous keys we'd also find that it contains 7 sharps, and they are: F, C, G, D, A, E, B. So now as well as an E#, we now have a B#. Double trouble! But we talked about A# so we have to journey further up the ladder of insanity. The next key would be G#, which according to our formula must contain 8 sharps. But there are only 7 scale degrees, and we sharpened all 7 for C#. And if we look at the fifths: F, C, G, D, A, E, B, the next one is F again. So what's going on. The fact is that the seventh scale degree is always a semitone below the root. So in the case of G#, this means that F's are double sharp ##. Hey Presto! 8 sharps! You can continue alone if you want to move through D# and onto A# if you like. I'm bailing out here. Hopefully that cleared a few things up.

28 comments sorted by best / new / date

    I didn't understand it all, but I think it's well written and one day I will understand it to the tee. Hopefully everyone will. Is your infomation correct? I'll trust you, that it is.
    ACFCPatrick wrote: the keys of G#, D#, and A# do not exist. as it would be much more beneficial to just call them Ab Eb and Bb.
    They do exist, but since the key signatures are written with flats its much more preferable and less confusing to name them with flats.
    Hey Thanks dude I understand it!!! Im a sound Engineer and a guitarist and now I understand Key Signature thanks buddy
    link no1
    i tried reading this and it just boggled my mind but it is 2 in the morning but on another note, it is well written and i would understand it perfectly if i wasnt so damn tierd
    Well if you do continue in the direction of C# into 8+ sharps then those are basically theoretical keys by then. But C# is used and i've seen some peices that do use it.
    B-E-A-D-Greatest-Common-Factor is how I remember flats, then just think of it in reverse for sharps. C# is at the bottom of the circle of fifths, so i'm not quite sure what you were trying to say there. Also when it comes to invervals it does matter if you say Bb or A#. G to Bb is a minor 3rd, G to A# is an Augmented 2nd
    Sharps: Fat-Cat-Goes-Down-Alley-Eating-Bread Flats: B-E-A-D-Gum-Candy-Fruit Those are the acronyms I learned to help remember it. I still use those.
    It's worth noting that sharped notes and flattened notes are different notes entirely, and that's why there's all the semantics regarding key signatures that a lot of guitar players don't understand because they play a tempered instrument. On cellos, on violins, on trombones, on non-tempered instruments, flattened notes and sharped notes are two completely different things and are played as such. That's why it matters whether you write Bb or A#. It's just not a very apparent trend on the guitar.
    I just asked my music teacher, what it means to be in the key of A and he gave me a big explanation down to how many wave lengths there are in each note. So this really helped me thank you.
    I just skimmed it, but this looks like a great lesson. My jazz piano teacher used to make me do chords in the "Circle of Fifths", covering every key. It looked similar to that.
    TheCyanideFire wrote: a bit of an oxymoron. But wo there horsey. your english confuses me mind
    So does yours mate... 'me mind'???
    Good lesson by the way. And for those of you who still don't understand key signatures, just join your school's band
    chris flatley wrote: as for the serious question about which sharps are in D, it's easy. work out how many miles it is to, for example Spain (doesn't matter where you live; all countries are the same distance away). Then you divide it by the corresponding letter position in the alphabet (in the case of D, it's5). Then you ask the oldest member of your family what is their favourite number and add it to the running total. Then write the answer on a piece of paper and put it in a foil tray, together with an egg and a tomato, and put them all into the microwave. Then while you're in the repair shop ask the guy behind the counter if there are any good music stores in the area. Buy a Bob Dylan chord book and find a song in the key of D. Rip out the time signature and take it to school on the day of the test. Bingo!
    L to the M to the A to the O!
    I got the sharps and flats order down, but does anyone know a good way to memorize which key signatures have which flats? Like for example, my music teacher gives me a test and asks me to write the key signature for D. How do I know how many sharps/flats I need?
    Just memorize the order of sharps and flats with this phrase. For sharps: (F)ather (C)harles (G)oes (D)own (A)nd (E)nds (B)attle Flats: (B)attle (E)nds (A)nd (D)own (G)oes (C)harles' (F)ather Takes practice.. When I first learned it it confused the hell outta me but just test yourself on some linepaper.
    sg dude 38
    our band teacher gave us acronyms to memorize the orders of the sharps and flats. for flats, its b,e,a,d,g,c,f, or "Betty eats apples during gym class friday." for sharps, its the same way, opposite order. try "fine christian girls dine at eddie's barbaque." or, you could even make up your own that work better. anyway, just thought i'd help you out.
    ACFCPatrick wrote: the keys of G#, D#, and A# do not exist. as it would be much more beneficial to just call them Ab Eb and Bb.
    Just cuz it's "more beneficial" to call A# Bb, doesn't mean there is no A#. You could even call B A##. It's not common but it's do-able. ANYWAY... Good article! Makes me wanna memorize the circle of fifths. I'm always confused about what order to put #'s and b's when writing out the key sig.
    ACFCPatrick wrote: the keys of G#, D#, and A# do not exist. as it would be much more beneficial to just call them Ab Eb and Bb.
    This is just stupid. G#, D#, and A# exists. And Wheter you want to call them Ab, Eb, and Bb, is mostly up to you.
    the keys of G#, D#, and A# do not exist. as it would be much more beneficial to just call them Ab Eb and Bb.