First is the Shanghai piano tuning and then adjusts the reference sound group. The adjustment of the reference group usually adopts the fourth-fifth cycle method to feel the beating between the fourth and fifth intervals by hearing (the beating is the sound that starts to appear when two keys are pressed at the same time. The change in strength, from the strong wave at the beginning of the sound to the time it goes down) There is a slight difference in the number of beats per second between the fourth and fifth intervals, and the beat notes between the fourth and fifth intervals are slightly different than those between the fifth and fifth intervals. A little more, this difference is hard to hear from the auditory sense (but the tuner can reflect it). This error is allowed, so in actual tuning, the interval between four and five degrees is basically a half beat per second.
The twelve semitones can be adjusted by mastering this rule, but it should be noted that in the process of adjusting the equal temperament reference group, the three strings in each homophonic group must be very pure and have no beat notes. Otherwise, accurate equal temperament notes will not be produced. After the twelve tones of the reference sound group are tuned, you can adjust the high range and low range according to the octave method. The treble region is characterized by short strings, high frequencies, and short sound duration, so the speed of keystrokes must be increased. The characteristics of the bass area are string length, large amplitude, low frequency, and strong overtones, so it is more difficult to distinguish the pitch, so the keystrokes should be slow and lighter, which can weaken the impact of overtones on hearing. After the piano's temperament is fully tuned, it will sound very comfortable to play, but this feeling of harmony and purity of each tone is inconsistent with the precise data tested by the frequency measuring instrument.
The actual measurement proved that the law of the sounds that sound very harmonious is that the high pitch is higher, that is, from the C2 sound in the second group of small characters to the C5 gradually higher