Sign on the Dotted Line
OK, so there's no dotted line, and a key signature will never be found at the bottom of an official document... but they are nevertheless very important. Without a valid signature, it is impossible to read sheet music accurately.
Think of a key signature as a starting point. It will tell you the 'frame of reference' you need to have in order to understand the notes on the staff lines, and especially how they relate to one another.
That's because notes in any given key signature are all in the same note-family. It's like a surname for every note in the scale.
Not Your Typical Family Reunion
Ahh, families. Often a great source of stress and friction. But notes in the same key-signature are a collection of relatives that play nicely together. Each note sounds pretty, or at least, acceptably disonant with the other notes in this collection.
The most common key signatures have the fewest number of sharps and flats. For example:
- C - no sharps or flats
- F - one flat
- G - one sharp
- D - two sharps
- Bb - two flats
Key signatures never have both sharps and flats. It's one or the other.
What They Look Like
You'll recognize a key signature by the sharps or flats assembled along the left side of the staff lines. Every line should have the key signature reinterated, just so there's no question what key we're all playing in.
There's a special order for these flats or sharps, but that doesn't matter now. What does matter is that you can figure out the key name by looking at this signature.
Finding the Key Name
Unfortunately, the key signature isn't written in plain English. Rather, we need to count the numbers of sharps or flats in the signature to determine the key name. There's actually a system for this, called the 'circle of fifths' which we'll get into later.
But for now, use this cheat:
For Key Signatures with Flats
The name of the key signature is the name of the second last line the flat is on.
Example: three flats - the second last flat will be on the Eb space, making it the key of E flat
For Key Signatures with Sharps
The name of the key signature is one half-step (one space or line) up from the last sharp.
Example: four sharps - the last sharp will be on the D# line, and one half-step up from D# is E, making it the key of E!