Who would’ve guessed?
Set the vibration in motion and press it to your skull close to the entrance to your ear and you’ll get the perfect perception of a 440 Hz A that people have always asked you to deliver when you mentioned or they estimated that you wanted to sing.
So what is it? The A on the high E-string of your guitar? The A the current day most common tunings are set to? Well, officially. Be cool, walk out of line, but play in tune.