(1) The great 440 Hz conspiracy, and why all of our music is wrong: Alan Cross – National | Globalnews.ca

If musical performances were to sound the same the world over, some standardization was required. As early as 1885, the Music Commission of the Italian Government declared that all instruments and orchestras should use a tuning fork that vibrated at 440 Hz, which was different from the original standard of 435 Hz and the competing 432 Hz used in France.

Source: (1) The great 440 Hz conspiracy, and why all of our music is wrong: Alan Cross – National | Globalnews.ca