Brief History of the Music Scale
All musical cultures have one common element – the interval of the Octave. An octave is the distance between 2 pitches where the higher pitch has 2 times the frequency. For example, concert A 440 Hertz is an octave higher than A 220 Hz, and an octave lower than A 880 Hz.
Interval: The distance between 2 notes with different
frequencies, i.e. distance separating 2 different
notes. Three prime intervals are the Octave (8va),
the Perfect 5th (P5) and the Perfect 4th (P4).
Semitone: The smallest division between notes – 1/12th the
distance of an octave. There are 12 semitones per
octave. Also known as a Half-Step.
Tone: Two semitones, or 2 half-steps. Also known as a
Whole tone or Whole Step.
Octave: The distance between 2 pitches where the higher
pitch has 2 times the frequency - 12 semitones.
Diatonic Scale: The 7 tone scale leading up to an octave comprised
of 5 tones and 2 semi-tones.
In ancient Greece, Pythagoras is attributed with using the prime intervals of the octave, the P5 and the P4 to break the octave into smaller harmonious intervals. Pythagorean tuning influenced music in the middle ages and Renaissance periods where the Catholic Church started to formalize the scale we now know as the Major scale, a diatonic scale building up to an octave.
The octave has been divided into 12 separate pitches before the starting pitch repeats at the octave. Many cultures have separated the octave into a different # of pitches. Chinese also break the octave into 12 pitches to match the twelve zodiac signs, but the tunings of the 12 pitches is different from the Western 12 tone octave. Persian music separated the octave into 24 pitches, while Arabic culture divided it into 16 pitches. Regardless, the breaking of the octave into smaller units is what separates music from different cultures from each other.
The selections of which pitches to use to create the 12 separate pitches, or which pitches to use for the 7 pitches of the diatonic scale, is a matter of the different tuning methods some of which in use today are Equal Temperament (ET), Just Intonation, and Pythagorean Tuning. There are arguments for and against each method, but it is Equal Temperament that predominates western popular music.