A couple more comments...
Although virtually all music is tuned to A=400, most songs use a subset of the available notes, so
some songs won't have any 'A' notes.
All real-world sounds have harmonics and overtones so you rarely find a pure 440Hz tone in nature. Different instruments have different harmonics & overtones and that's why a guitar playing an 'A' sounds different from a saxophone playing the same-exact note, and its the reason that two different singers sound different when singing the same song.
Most music contains several simultaneous notes on multiple instruments with thousands of harmonics and overtones (which you can see if you look at the spectrum).
Many horns & woodwinds can't be re-tuned (because pitch depends on the length of the "tube"). Pianos take a long time to re-tune.
So in most cases it not practical to use non-standard tuning. (A rock band with just guitars, bass, and drums, can easily do it.)
However, it is easy to change the pitch of a recording up or down by changing the playback (or recording speed) on a tape recorder and there are stories of songs being accidently mis-tuned back in the analog tape days. It's not that unusual for amateur recordings to get out-of-tune when using a regular consumer soundcard. Of course it can be done intentionally (with digital or analog).
Most people can't tell the difference between A=440 and A=432 without a reference. For example, a musician will notice that their instrument isn't in-tune with the recording if they try to play-along with the recording. Or, 1 out of 10,000 people have
perfect pitch (AKA absolute pitch) which means they can identify/name the note being played and they
might notice that it's "off". But "perfect pitch" isn't really perfect and 432 is close to 440, so they'll probably just hear it as a regular 'A'.
You can generate 432 or 440Hz tones (or any frequency you like)
Generate menu.
Chart of musical note frequencies