Music uses the alphabet from letter "A" to the letter "G." Considering there are far more frequencies of sound, musicians repeat the letters in a continuous cycle from the lowest possible frequency to the highest. There are, therefore, many sounds that receive the letter designation "A." Musicians refer to the letters used in music as pitches. When constructing musical scales, musicians use each pitch only once.
An octave in music is the distance between two sound frequencies that share the same letter. Mathematically, the frequencies match this movement. The most common pitch is "A," which has a frequency of 440 hertz. The frequency of the next highest "A," one octave higher, is 880 hertz. The frequency of the "A" one octave below is 220 hertz. The purpose of a musical scale is to ultimately provide the listener with the ability to hear this octave movement with gradual changes in sound frequency.
To achieve a change from one octave to the next, musicians have developed a method of changing frequencies gradually in a series of steps. Musical scales have two different types of steps. Generally speaking, a whole step is a 48-hertz difference from one pitch to the next. The other type of step, a half step, is around a 24-hertz difference from one pitch to the next. Placing the whole steps and half steps into a variety of patterns is how musicians develop musical scales.
To give music the sense of movement, each piece of music must have a pitch that acts as a starting and stopping point, or tonal center. Musicians can use any pitch as the tonal center of a song through the use of musical scales. By arranging a pattern of half steps and whole steps, musicians are able to help the listener determine where a song begins and when it ends.
The most common musical scale, from the beginning of recorded history to the popular music of today, is called the major scale. The major scale uses two whole steps and a half step followed by three more whole steps and a final half step. The placement of the half steps is critical to establishing a tonal center in the listener's ear. If you rearrange the placement of the half steps, you alter the tonal center. Other scales that are not as common as the major scale create their tonal centers in this fashion.