so apparently the treaty of versailles, the treaty that ended world war one, also included a clause saying that all signatories would require that the note called concert A (today usually 440 Hz) be tuned to 435 Hz in professional orchestras
how the hell did that make it into the treaty of versailles, it seems like a non sequitur
long
@starkatt @keisisqrl important for context is the fact that this predates 440 Hz being concert A; at the time, concert A could vary quite a bit and some orchestras, wanting a brighter sound, tuned as high as 455 (though we've seen anecdotes of ones over 500!) but singers with strained voices were trying to get it standardized to 420 or even lower so at some point around the late 19th century France, being France, made a standard tuning fork and wrote it into law that orchestras had to use this 435 Hz compromise
Other countries did not follow suit though until the treaty of versailles forced them to and even then, the UK sneakily used temperature differences to tune their A to 439 Hz (the tuning fork was specified at 15°C. the london orchestra tuned their oboes to 435 Hz at 15°C, which translates to about 439 Hz at the temperature they performed at, and the oboes were used as the reference for tuning all the other instruments) and this eventually won, though it was tweaked to 440 since 439 is inconveniently prime