Why Do We Need Key Signatures?
The major and minor scales have a fixed series of intervals. Fixed, meaning, it doesn’t change - it’s the same every time. Each major scale will have the following intervals on its given starting pitch:
whole step
whole step
half step
whole step
whole step
whole step
half step.
It doesn’t matter if your major scale starts on C natural, or F flat down three syntonic commas, they all have that exact same set of intervals.
A natural minor scale will always be whwwhww, no matter the starting pitch.
Of course, when we write out those scales in a piece of music, we have to include every accidental - which depending on the key, can be a lot to look at - like F# major. It’d be really nice to 1) not have to write all those accidentals, 2) not have to read all those accidentals.
Every key has a unique number of sharps or flats. Unique Like a Signature. Only G major features an F# and a C natural. Only Ab major has a Db and a G natural. But, notice I said, a unique number of sharps or flats. When building major and minor scales we only use each letter name once. Which means in the key of A natural, this leading tone can’t be called Ab, we’ve already used A, so it’s called G#. The first two notes of the Db major scale is Db and Eb and not Db and D#. That way our scales look nice and even, and not enharmonic chaos.
And since every key has a unique number of sharps or flats - instead of having to list every note - we can use a shorthand, where we only list which accidentals are members of that key - and this is called a Key Signature. It goes over here on the staff at the beginning of every line. If we have four sharps, that tells me that we have F, C, G, and D sharp, and everything else is natural. Or, maybe 2 flats. This tells me that B and E are flat, but everything else is natural. This also has an added bonus: we only use accidentals for notes that aren’t in the key, letting the reader know that something’s different. Something that would be harder to see if all accidentals were written out.
And if you’d like a handy chart so you can keep track of all of this, you can get this chart for free by joining my email list; where not only will you be the first to know about new videos and projects, but you’ll also have access to more of these music resources. Click on the chart below, and then scroll down to “Get this resource for free”.
One other thing to note: Each major scale shares its key signature with a minor scale - also known as the relative minor. The relative minor is always the sixth scale degree of the major scale.
