How to Read Musical Key Signatures
Tones & Semitones
On the piano or keyboard a semitone is the distance between any note and the very next one, regardless of their color. A tone is made up of two semitones. The distance from the note E to the note F is a semitone, because there are no other notes in between. The distance from A to B is a tone, because there's a black note in between.
If you've never tried it before, reading music can be a real challenge. One of the most difficult things to get under your belt when you start is the concept of keys and key signatures. Faced with 7 sharps or flats it can be tricky to try to work out exactly what you're supposed to do.
Sharps and flats get their names from the way they're used in the music. Sharps raise a note by a semitone, and flats lower a note by a semitone. In practice that means the following:
- A sharp in front of the note F turns it into F sharp
- A flat in front of the note B turns it into a B flat
Recognizing Key Signatures
When the sharps or flats appear at the beginning of a piece of music, we call that its key signature. When they appear in the music, we call them accidentals.
If there are no sharps or flats, you're in the key of C major. The key of C major goes from one C up to the other, using no black notes.
If there's a G sharp written into the music, that's an accidental. It's there to tell you that the key signature (no sharps, no lfats) belongs to the relative minor of C major, which is A minor. G sharp is A minor's leading tone.
Key Signatures and the Circle of Fifths
Keys and key signatures work on what's known as the Circle of Fifths. If you go up 5 notes from C, you come to G. G major is the first sharp key, with one sharp. The sharp in G major's key signature is F sharp, the leading tone. Keys with more than one sharp also include the leading tone, as well as other sharp notes as required.
For flats, work in the opposite direction. If you go 5 notes down from C, you come to F. F major is the first flat key, with one flat.
That's easy enough when the key in question has only one sharp or flat, but what about when there are lots of them?
To find the key of a piece with five sharps, for example, simply work it out using the Circle of Fifths. Here's how to do it:
- 5 up from C is G (one sharp, which must be F sharp, G's leading tone).
- 5 up from G is D, which will have F sharp but also C sharp, its leading tone.
- 5 up from D is A, with three sharps, F, C, and G.
- 5 up from A is E, with four sharps: F, C, G, and D.
- 5 up from E is B, with five sharps: F, C, G, D, and A.
For Flats Work Down the Keyboard
To find the key when there are loads of flats, do the same working in the opposite direction. A key signature with 5 flats, for example, means you have to work down as follows:
- 5 notes below C is F (the first flat key with 1 flat)
- 5 notes below F is B (the second flat key with 2 flats), which is obviously B flat
- 5 notes below B flat is E flat (3 flats)
- 5 notes below E flat is A flat (4 flats)
- 5 notes below A flat is D flat (5 flats)
There can be seven sharps in total (which makes the key of C sharp major). They always follow the same order, which is: F, C, G, D, A, E, B -- each one 5 notes higher than the one before. The order in which the flats appear in a key signature is the same thing BACKWARDS - B, E, A, D, G, C, F.
Keys & Key Signatures
B flat major
E flat major
A flat major
D flat major
F sharp major
G flat major
C sharp major
C flat major
Working Out Key Signatures
Here's an example of how to find out what key a piece is in just by looking at the key signature.
We know the order in which the flats appear is B, E, A, D, G, C and F. A key with four flats in the key signature, then, would have to include B, E, A, and D flats. To find out which key that puts the music in, just back up one, or go back to the second-last flat listed in the series. So the key with four flats would be - A flat major.
To work out a minor key, count the sharps or flats as above, and then check for accidentals (an extra sharp or natural written in the music). So, for instance, a piece with 3 sharps could be in the key of A major or its relative minor, F sharp minor. If it's the latter, there'll be E sharps written in the music as well.
Likewise, a piece with three flats will either be in the key of E flat major or that of C minor. If there's a B natural written in, it's most likely going to be C minor, with B natural being the raised leading tone.
Until you get used to reading key signatures, copy or print out the Circle of Fifths to make it a bit easier. As with everything else in life, practice makes perfect, and to give you a little more practice - try the quiz below!