“Countries, and even cities, each set their own criterion, with the result that tuning varied widely from one locale to another”: How 440Hz became the “concert pitch” – and the argument to change it to 432Hz

Does tuning music to A = 432 Hz versus A = 440 Hz have a measurable effect on listeners?

432 vs. 440: The Ultimate Guide to Tuning Standards

Sound Waves – Mathematics of Music