Although the staff appeared in the13rd century, the Gregorian chant in the church still maintained the staff. Guido found that the familiar St. John's hymn began with the scales from low to high, C, D, E, F, G and A. In order to teach students the relationship between solfeggio and semitone, he taught them to sing these six sounds with the Latin syllables ut, re, mi, fa, sol and la at the beginning of the hymn rhyme, so roll call appeared. Later generations just changed ut to do and added si to la.

This is because the average rhythm of 12 is not a natural melody (also called pure melody), but a mathematical melody. In order to simplify symbols and performance, the absolute pitch of each tone has been adjusted. The pentatonic scale used in ancient China is a natural melody. People in other parts of the world don't all use the same seven tones or some of them.