The scale originally used in Western music is a set of seven pitches within the octave, called the diatonic scale. Dating from ancient Greek times, the diatonic scale is still in use today. When the first of the seven pitches is repeated at a higher duplicating pitch, the total is eight — hence the name octave, meaning “eight span.”

Anyone who knows the series do re mi fa sol la ti do is at home with the diatonic scale. You can count out the octave for yourself starting with the first do as one and ending with the second do as eight. The set of white keys on a keyboard plays this scale. Shown in the following diagram is a keyboard and diatonic scale notes running through two octaves. The scale notes (pitches) are marked with their conventional letter names. Because there are seven pitches, only the letters up to G are used before returning to A.