Now, let’s be sure we are clear on the word octave.
The octave (eighth in Latin) is the interval between one musical pitch and another within which its frequency is doubled (higher) or halved (lower).
Frequency? Yes, all music notes have a set frequency and are measured in frequency hertz (Hz). Hertz is a unit of frequency and is defined as one cycle per second. A note gets its pitch by how many times (cycles) it vibrates per second.
When tuning instruments it is common to use a reference note of A = 440 Hz. This note is the A in the center of the keyboard. Orchestras for example tune using A = 440 Hz as a reference.
So, when playing the A in the middle of the piano the string vibrates 440 times per second.
The C in the middle of the piano = 261.6 Hz
One octave below middle C = 130.8 Hz
One octave above middle C = 523.3 Hz
We rounded off the numbers in the above graphic just to make the below math a little more clear.
Notice that if middle C is 260 Hz
Half of that (260 Hz ÷ 2), would be the octave below 130 Hz
Double that 260 Hz x 2), would be the octave above 520 Hz
Again, the octave (eighth in Latin) is the interval between one musical pitch and another within which its frequency is doubled (higher) or halved (lower).
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