There is a definite relationship between key signatures and major scales. We will explore that today. You will learn how that relationship works!
First, a review of Key Signatures:
Key signatures tell us what scale a piece of music is based on.
Key signatures tell us what notes are always sharp or flat in a given piece of music.
Always read the sharps or flats in a key signature from left to right. And they will always be written in the same order.
Key signatures always have the sharps and flats listed in the same order. They always follow the same pattern.
Notice how one listing is the exact opposite of the other! Now, compare the listings here to the key signatures shown above. Notice how they read left-to-right.
You can find the name of the major scale from its key signature. Here are a couple ways to do that:
Just memorize them
Key Signature with sharps – Find the name of the last sharp, go up a half step, that is the name of the major scale, or the key the piece is in.
In the D Major key signature you can see there are two sharps. The last one (reading left to right) is the C#. If you go up a half step from C# you are on a D – and that is the name of the key.
In the 2nd example, E Major, the last sharp is D#. Up a half step from D# is E. The name of the key is E Major.
Key Signature with flats – The second-to-last flat in the key signature names the key.
B Flat Major Key Signature
Look at the example on the left, the key signature with 2 flats. Look for the 2nd-to-last flat. It is a B flat, so our key name is B Flat Major.
In the other example, the one with four flats, again, look for the second-to-last flat. In this case it is an A flat. So the key name is A Flat Major.
Next, a review of Major Scales:
All major scales follow the same pattern of whole steps and half steps. Remember what it is?
It doesn’t matter what note you start on, the pattern must be the same to make a major scale.
Use accidentals (♯,♭) to adjust the notes to fit the pattern.
Remember, each note in a major scale must have a different letter name.
You cannot have F, then F♯ in the same scale. But you may have F – G♭. Even though on a keyboard F♯ and G♭ are played as the same note, you must have different letter names in a scale.
Now – The Relationship between Major Scales and Key Signatures
The accidentals you use to make a major scale fit the right pattern become the key signature for that scale. Here are some examples of what I mean:
Now, if you are looking at a key signature, you can use the information I showed you earlier to find the name of the key. The name of the key is the starting note for your major scale. The sharps or flats in the key signature get applied to the notes in your scale to make it fit the pattern for a major scale.
Do you see now how the key signatures and scales are related? Any questions? Let me know in the comments!