The white keys and black keys on the piano keyboard are arranged according to a fixed rule, and the sound with a fixed height on each key is the sound name

Modern music uses seven English letters C D E F G A B (or its lowercase) to mark the sound name.

The pitch distance between the adjacent sounds of these seven different high and low tones can be divided into semitones and whole tones, in which the relationship between E and F and between B and C is semitones, and the relationship between the other adjacent sounds is whole tones.

when the seven basic tones of p>C D E F G A B change by a semitone, if they are higher than the original ones, they are indicated by a sharp sign (or a sharp sign) (#); A semitone lower than the original, represented by a flat sign (or a flat sign) (ь); The rising two semitones are indicated by the double sharp sign (×); A drop of two semitones is indicated by a double drop sign (ьь). If the raised or lowered tone is to restore its original pitch position, it is indicated by a prime sign (□).

the sound name is necessary, CDEFGAB, because the problem of tone will be involved in the future.