What you are talking about is temperament, which refers to the method of determining the pitch and relationship of each note in the music system, as well as the mode. Common ones include "the temperament of fifths", "pure temperament" and "twelve averages" "Twelve equal temperament" is used in most of the current music, because it is very convenient to modulate, so not only the piano, but also the orchestral instruments in the band are often tuned according to the twelve equal temperament instead of pure temperament, so you ask The question is wrong. Only different scales and modes are used in music. For example, pentatonic mode is commonly used in ethnic music, blues mode is used in jazz, etc.

The law of mutual generation of fifths refers to the generation of a uniform law based on the relationship of pure fifths, that is, the fundamental tone is pushed upward by a pure fifth each time

The pure law is based on the pure fifths, plus The previous major third is used as the element of temperament, thus producing seven basic pitch levels

Twelve equal temperament means that the octave is divided into twelve equal parts, and each note is higher than the previous one. 1.0595 times

For specific details, you can check "Lyxology" or basic music theory.