In response to Harvey Chao's valid question about vertical pianos
and how they retain their tuning.

Well-constructed vertical (upright) pianos have several large and
heavy reinforcement posts that provide strength and stability to
the sound board.  A look at the rear of almost any vertical will
reveal the usually four or five posts that typically measure and
look like a four by four vertical beam.

The case of the usual vertical piano gives little, if any, support
to the stability and, indeed, it may be observed that the case may be
removed from a vertical piano and not destroy the tuning.

If I had to describe the stability of a vertical piano I'd probably
call it the 'brute force' or 'rock solid' method as compared to the
'guess and by golly' system of the 'square', the 'other rectangular'
piano.

'Over-stringing' was considered an improvement in stable tuning but
I've never heard of it being referred to as 'grand' anything, nor does
it make a "grand" out of any piano.

There are several good texts available to serious piano tuners that
detail and give a general history of the development of the
"piano-forts" from the technical point of view.

Hal Davis