I'm not entirely sure what this question is asking.

The frequency of a specific notes is somewhat arbitrary, and has shifted around through history. An A is 440Hz, but has drifted as low as 380Hz and as high as 480Hz. Like most standards, A=440 is for the purposes of interchangeability.

As to scales, the most important intervals are not arbitrary, but have a basis in physics. The octave is a 2:1 ratio, the tonic or 5th is 3:2, the subtonic or 4th is 3:4. When notes at whole number ratios are played together they resemble the sound and overtones of a larger instrument with rich harmonics.

Both eastern and western music picked up the notes of these intervals to form pentatonic scales.

The 12 step chromatic scale is a somewhat of compromise for the benefit of keyboardists. Although microtones happen a lot in eastern music, they happen quite a bit in western music as well.

• Players of the oud use more than 12 notes. Here is a nice example http://www.youtube.com/watch?v=24A6MDVeXUs

• Violin players know that the 7th "leading tone" can be a little shaded upwards.

• Whammy bars.