Octave and Registry Ranges

 Each note has its own pitch, but as we saw, there are only so many different notes (there are 12 in the Western music system). This doesn’t cover the whole range that our ears can hear. That means that those notes have to repeat in higher and lower registers. All registers contain the same 12 notes, repeated both in higher and lower pitches. When a note repeats in a higher or lower register—when it has a different pitch but is the same note—we say that the distance between those notes is measured in octaves. An octave is simply the distance between one note and that same note repeated in the next higher or lower register on the frequency scale. Physically speaking, an octave is the distance between two pitches that results in one pitch having exactly twice as many waves in the same amount of time (number of oscillations per second). In other words, the frequency of a note that is an octave up from another note is twice that of the first, meaning that there are twice as many waves, and the pitch is higher despite being the same note. Between any two octaves there are all of the notes, and the order of the notes stays the same. What that means is that if you understand something in one octave, you have understood it in all of them. If you look back at the note circle (Figure 2) you can see that an octave is equal to going one full way around the note circle from any starting note. If you go clockwise and end up on the same note you would get an octave higher note, and likewise if you go counterclockwise you would get an octave lower note. After one octave, the notes simply repeat themselves in the same order in the next lower or higher octave/register. Note that the terms ‘octave’ and ‘register’ are often used interchangeably. An octave can also be viewed not just as the distance (interval), but as a single note—the eight note—which has the same letter name as the first note, but double the frequency. This will be important when we get to scales and chords later in the book. Limited by what our instruments can produce and the range that our ears can hear, there are only so many registers (or octaves) at our disposal. Different instruments vary a lot in their ranges; some instruments, such as pianos, have many octaves, so that even though there are only 12 notes there are 88 keys on a full-size keyboard (88 different pitches that can be produced, which is as many as 7 octaves). Here’s a picture of a full size master piano keyboard with marked all C notes repeated in eight different octaves/note registry ranges.

Figure 3: An octave with the middle C is called the Middle octave—it’s the 4 th octave on a full size piano keyboard You may have seen before a note with a number next to it and wondered what that number means. Unless we’re talking about a particular chord, that number tells us what kind of registry range the note is in. Looking at the figure 4, you can see that there are eight C notes on piano, and this number (1-8) tells us exactly which C to play (in what registry/octave range). Same goes for any other note; for example, D3 means that this D note is in the C3-C4 range, or the third range. This is especially important when writing down music using notation because it determines what kind of clefs we will use to best cover the range of a piece, and minimize the use of ledger lines (this is explained thoroughly in How to Read Music for Beginners book).