[RightWhale]

one hundred pianos all tuned to the same fork are automatically tuned to each other?

There is another truth available to those with subtle hearing. When a piano is moved its tuning changes. Imagine 6 billion pianos in various conditions and various states of repair and use moving constantly.

[unspun]

There is another truth available to those with subtle hearing. When a piano is moved its tuning changes. Imagine 6 billion pianos in various conditions and various states of repair and use moving constantly.

That is why we all need to be in touch with the source of tuning, as well as the tuner.