https://www.youtube.com/watch?v=LjR0WpWwLrE
https://www.medson.net/A432hz-myth.html
Few historians have realized that the tuning fork is actually a modern problem that does not exist earlier than the 16th Century, and that the oldest western music, like most music of the world, just did not know the concept of tuning fork.
The researches done by renowned musicologists and academics on the musical tuning, prove beyond any doubt that:
¤ There was no standard for establishing a referential frequency for the 'A' before 1859 (435 Hz) and 1936 (440 Hz).
¤ The 432 Hz frequency of the 'A', which we will discuss here, is not a standard and seems never to have been used in preference to other types of frequencies. We read about it only once among the 1'500 references cited by Bruce Haynes, on the St-Jean-Baptiste church organ, in Magnano, Italy, 1794.
¤ The 435 Hz 'A' was in use in Paris in the 19th Century.
¤ The 440 Hz 'A' was not created by the Nazi regime, as it was already in use before 1670 in Holland, between 1730 and 1770 in Italy and England, between 1770 and 1800 in France, and from 1700 in Germany.