The 432 Hz vs 440 Hz Tuning Debate Is Largely a Myth

A widespread belief holds that modern music tuned to 440 Hz is harmful, while 432 Hz is "natural" or "healing." There is no scientific evidence for this. Standard concert pitch (440 Hz) was internationally adopted in 1955 for practical interoperability — before that, tuning varied widely across regions and eras. Mozart's instruments were likely tuned to around 422 Hz by modern standards.

Source: Journal of the Acoustical Society of America; various music history sources