In this post we will learn about the double sharp sign in music theory, it’s purpose, usage and how to read it on sheets music.
A single sharp sign instructs you to raise the note by a half step but the double sharp is slightly different. The double sharp symbol is the equivalent of two sharps. A sharp sign raises a note by one half step, and a double sharp sign raises a note by two half steps (one whole step or a tone).
How a Double Sharp Work?
Western music contains 12 different pitches. These twelve pitches can then be repeated over different octaves.
There are seven of these pitches that are considered ‘natural’, these are:
A B C D E F G
The remaining 5 pitches are then either sharp notes or flat notes. However, sharps and flats are not the only accidentals you will see in music. We can also have double flats and double sharps.
Double sharp notes are notes that sound two half steps (one whole step) lower than what we usually see on the musical staff.
The notes on the treble staff are:
F A C E in the spaces going from bottom to top.
E G B D F on each line going from bottom to top.
Each of these notes can be altered to become a double sharp i.e. two half steps higher. This is very easy to visualize on the piano keyboard. It is easy to think of the white keys as your natural notes.
Look at the note C on the piano keyboard below. For us to turn this into a C double sharp, we must move up by two half steps. This takes us from the white key to the black key back to a white key.
But how do we show this in sheet music?
We use a special sign to show that the note should be lowered by two half steps.
What is the double sharp sign in Music?
Drawing a double sharp sign
To indicate that a note should be a double sharp note we use a double sharp sign. A double sharp symbol resembles small letter x.
This symbol should be written in front of the notes that you wish to be double sharps. This is because the performer needs to know before they play the note, as a double sharp raises a note by two semitones (half step).
Using key signatures
It is extremely important to note that we do not use double flats or double sharps in a key signature. In a key signature we only see single sharps or single flats.
A sharp key will have sharps in the key signature and a flat key will have flats in the key signature. Remember this is the same for major scales and their relative minor key.
A double sharp sign will be used as an accidental. Even if there is a single sharp in the key signature you still need to use the double sharp sign, if you wish to double sharp the note. The double sharp symbol alters the sharp you have in the key signature.
This is the same if you have a flat key signature. If you want to double flat a note that is already flat from the key signature, you still need to write the double flat sign in front of the note.
Double accidentals and enharmonic equivalent notes
Double accidentals are extremely important when it comes to writing enharmonic notes.
An enharmonic note is a note that sounds the same as another note but is spelt differently. For example, C double sharp is the enharmonic equivalent of the D natural note.
Take a look at the piano keyboard and you can see why these two notes are enharmonic equivalent.
You will use enharmonic notes to make music easier to read, it is important to make sure you look at what key your music is in and this will help you decide what accidental you will need to use.
Cancelling a Double-Sharp sign
As with other accidentals, when you place an accidental on a note in a measure, this sign will only last for that one measure. As soon as the bar line appears, the accidental is cancelled.
If you would like the accidental again in the next measure, you will have to write it again.
If you want to cancel a single accidental within a measure, you use a natural sign.
Double sharp signs are a little different as there are two circumstances. You can of course use a natural sign to completely cancel the double sharp in a measure, but if you would like to return it to a single sharp, then you simply write a single sharp next to the note and this is sufficient to cancel the double sharp sign.
When Should You Use a double Sharp vs. a double Flat?
As a general rule you will use the double sharp sign when you are in a sharp key and a double flat when in a flat key.