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Section 1.3 Octave Registers

The note names used in music are \(\text{A}\)\(\text{B}\)\(\text{C}\)\(\text{D}\)\(\text{E}\)\(\text{F}\)\(\text{G}\) (known as the “musical alphabet”). After \(\text{G}\), the note \(\text{A}\) returns and \(\text{A}\)\(\text{B}\)\(\text{C}\)\(\text{D}\)\(\text{E}\)\(\text{F}\)\(\text{G}\) occurs again and again. The distance from the first \(\text{A}\) to the second \(\text{A}\) is an octave (which means the notes are eight steps apart.)
\(\text{A}\) \(\text{B}\) \(\text{C}\) \(\text{D}\) \(\text{E}\) \(\text{F}\) \(\text{G}\) \(\text{A}\)
\(1\) \(2\) \(3\) \(4\) \(5\) \(6\) \(7\) \(8\) (octave)
The distance from any note to a note of the same name in the next register above or below is called an octave (abbreviated “8ve”).
How can the piano keyboard have 88 notes when there are only seven note names? The musical alphabet repeats 7 times (with an extra \(\text{A}\)\(\text{B}\)\(\text{C}\) at the top), which means we have at least seven octave registers. (There are also five chromatic notes in each register, which we will learn about when we discuss Accidentals.) When learning about octave registers, we will focus on the note \(\text{C}\) for reasons that will soon become clear when we learn about the major scale.
We use octave registers (\(\text{C}_{4}\), \(\text{D}_{5}\), etc.) to specify the exact register of a note. The note \(\text{C}_{4}\) is known as “middle C” and is an important reference point. See the keyboard in the example below.
Picture of keyboard with C1 through C8 identified
Note that the register number changes after the note\(\text{B}\) each time (\(\text{B}_{4}\) is followed by \(\text{C}_{5}\)).
In treble clef, middle \(\text{C}\) is notated on the ledger line below the staff. In bass clef, middle \(\text{C}\) is notated on the ledger line above the staff.
Figure 1.3.1. Middle C (C4) in treble clef and bass clef
The other two commonly used clefs are alto clef and tenor clef. Each use a \(\text{C}\) clef that, when placed on a staff, designate the placement of middle \(\text{C}\).
Figure 1.3.2. Middle C in alto clef and tenor clef
The grand staff, which is a treble and bass clef joined together by a bracket, is how piano music is written.
Note that middle \(\text{C}\) is always clearly notated in either the upper or lower staff and never floats between the two staves.