Why are there 12 notes to the octave?

Question

Why are there 12 notes to the scale/octave in music. Why not 8, 10, 16 or 159?

Answer 1

Simply because that is how our standard pianos are built.  With many instruments, and especially when singing, you can in fact produce 1/2 tones  -  we could consider that there are many more notes in a scale.  

The scale begins at the next octave when the tons is the same as the first one, only higher.  Anything you can squeeze in between those two identical tones could be considered part of the scale.

Answer 2

Good info from the Wikipedia source above.

Just wanted to point out that this only refers to the Western, or well-tempered, scale (and also within the Western scale there are microtonal scales that have more notes).  

Other forms of scales have less (or more) notes.

Answer 3

There are eight whole tones (octave comes from octo, which is latin for eight) and there are four half tones, which makes 12 tones (or notes) to the octave.

Answer 4

The number of notes in an octave is 12 because to the human ear, the note twelve notes away from another sounds essentially the same as the first. (So, two notes that are 12 notes apart are given the same note name, A and A, for example.) This "sameness" has to do with the way our brains are wired and the way the notes are structured. Our musical instruments owe their design to the concept of the musical octave, not the other way around.

By the way, the word "octave" refers to the 8-note diatonic scale within the octave.

Hope that helps.