In Latin, scala means “ladder” and that original meaning applies to the musical scale.

The Encyclopedia Britannica says: “Scale, in music: any graduated sequence of notes, tones, or intervals dividing what is called an octave.”

A tone is any sound that can be recognized by its regularity of vibration. When you sing or play a musical instrument, you are disturbing the air around you and creating little wind storms made up of invisible waves. These waves go up and down at a regular speed. Our ears perceive the waves and transmit information about them to our brains, which interpret the information as a sound or tone, also called pitch.

The faster the waves, the higher the tone. Middle C on the piano, for example, vibrates at 261hz (waves per second). The low C string on a cello vibrates at 65hz, while the highest E on a violin moves at 5,274hz. Most people can hear tones as low as 20hz and as high as 20,000hz. (The abbreviation “hz” honors the man who first measured wave frequency, physicist Heinrich Hertz.)

When we want to make a record of these sounds by writing them down, we use symbols called notes. A note, as its name implies, is simply a written-out tone.

Just as we can divide and measure distance into inches and time into minutes, we can measure the distance between sounds. We call these distances intervals. And just as different cultures have devised different standards of measurement – think pounds vs. kilos or Fahrenheit vs. Celsius – different cultures have different ways of measuring the distances between tones.

Interestingly, all cultures seem to agree on one measurement – the interval whose higher tone has a sound-wave frequency of vibration twice that of its lower tone. For example, Western music uses the letter A to mean the tone vibrating at 440hz. When we hear the tone that vibrates at twice that speed, 880hz, or at half that speed, 220hz, our ears perceive all three to have the same quality of sound. Consequently, we use the letter A to mean any of these tones. This unique distance is called an octave.

But why do we use the word “octave” to describe this distance? “Octo” means eight in Latin – is that relevant here? Well, yes, because in Western music the most common way of creating tones between one A and the next A is to space six other tones in between them, which we call B, C, D, E, F, and G. When we add up the tones from A to A, the sum is eight: Seven unique tones plus the repeated one at the end equals eight. Octave means “eighth in a series” in the same way that fifth means “fifth in a series.”

OK, we’re getting very close to understanding a scale: It’s a series of musical tones which are separated into steps which take us from one musical point to another.

Now here’s where it gets interesting. On our musical ladder, the distance between each tone isn’t always the same.  The distance from B to C is only half as far as the distance from A to B. Same goes for E and F. We call those distances “half steps.” The others are whole steps.

The most common sequence of steps in Western music, is a C major scale, which works like this:

C goes up a whole step to D
D goes up a whole step to E
E goes up a half step to F
F goes up a whole step to G
G goes up a whole step to A
A goes up a whole step to B
B goes up a half step to the next C

The major scale is by far the most common scale in Western classical and popular music. But it’s not the only one! We can change the sequence of whole and half steps to make a minor scale. We can start a scale on any of the seven basic tones and make what are known as modal scales …. We can divide the whole steps into half steps and make a scale of twelve tones, known as the chromatic scale … we can select some but not all the twelve tones and make up special scales like the diminished scale … we can get rid of the half steps completely and use seven whole steps to make what’s known as a whole tone scale … or we can omit one or two of the seven basic tones and divide the octave with only five, six, or seven tones.

Whatever scale we make, the tone that starts and ends the scale becomes the tonal center of the music we sing or play and our ears perceive it as the most important tone.