The Octave
If you listen through both the male and female voice versions of the previous examples, you will notice that the sequence of notes is relatively the same. The male voice example is simply a lower version of the female voice example. These examples are one octave apart.
Although there are only seven different letter names used in music - A, B, C, D, E, F and G - there are various repetitions of these note names at higher and lower pitches. E.g., the following example demonstrates all the natural notes from A in the bottom space of the bass staff to A on the first ledger line above the treble staff.
This covers a range of three octaves. Every time you come to a new A note after going through all the other letter names, the new A note is in a new octave. Proceeding through all the other pitches, each of them is one octave above the previous note with the same name.
For example, middle C is one octave above the C in the second bottom space of the bass staff, the F in the bottom space of the treble staff is one octave below the F on the top line of the treble staff, etc. This is easy to understand by looking at the keyboard.
