﻿ Music Theory Octaves

### Notes and Scales

Musical notes, like all sounds, are made of sound waves.  The sound waves that make musical notes are very evenly spaced waves, and the qualities of these waves - for example how big they are or how far apart they are will affect the sound of the note.  A note can be high or low depending how frequently one of its waves arrives at your ear.  When scientists talk about how high or low a sound is they talk about frequency.  the higher the frequency the higher the sound.  Frequencies can be measured like 440 vibrations per second.

People have been making music long before we knew what sound waves and frequencies were.  So when musicians talk about how high or low a sound is they talk about the notes pitch.  And instead of numbers they give each pitch a letter name like "C".  Musicians call a note with 440 vibrations per second "A".

Octaves are the same note name but at twice the frequency.  So "A" at 440 VPS is an octave lower than "A" at 880 VPS.  Notes in different octaves are so closely related that when musicians talk about the not "C", it doesn't really matter which "C" they are talking about.  Because of this most discussions of music theory don't bother naming octaves.  Informally musicians may talk about "middle C" or  "G above the staff".

The octave is divided into twelve equally spaced notes.  If you played all of these notes you would be playing a chromatic scale.  Other music traditions like Chinese divide the octave differently so they have different scales than western music.

The word octave comes from the Latin meaning "eight".  So while we have twelve notes between octaves only seven are used in any particular major or minor scale.  the eight note is the octave above or below the beginning note.  These are "Diatonic" scales and they form the basis for most western music.  It is much easier to visualize using a piano keyboard where all white keys represent the seven letter notes of A,B,C,D,E,F,G, and the black keys represent the sharp or flat of each note.

Whether it is a pop song, a classic symphony or an old folk tune, most music that feels comfortable to western listeners is based on either a major or minor scale.  The other notes on the chromatic scale are used to sparingly to add interest or to change the key in the middle of the music.