Prime Octave

The A3-A4 octave is the Prime Octave.

It is easier to use the words ‘Prime octave’ than to continually say “the A3-A4 octave”.   So we started referring to the A3-A4 octave as the Prime Octave, and it stuck.  It was specific and easy.  The A3-A4 octave is the Prime Octave.

Same way with the A2/A3 octave.   We refer to the A2-A3 octave as the Sub Prime octave.

It would have been nice, if Scientific Notation would have been an A to A thing.  But it’s not, it’s C – C.   If it was an A to A thing, we could simply refer to the 4th octave or the 3rd octave and everyone would know which notes we’re talking about.  But technically the 3rd octave is C3 – B3, the 4th octave C4 – B4 and so on.

Calling A3-A4 the 4th octave is not technically correct.   So we refer the A3-A4 octave the Prime octave and the A2-A3 octave the Sub Prime octave.