I too would be interested to hear any comments on the Viennese
piano action from those who have played or regulated it.  I'm
surprised to hear of it being built after the early 1800s, and
a Boesendorfer with it would be quite valuable.  Modern reproductions
have been made of Viennese action "fortepianos", which have been
used in recordings of Mozart and early Beethoven sonatas, for
which they may be preferable.

What I do know is that this action is very simple and reliable,
but with no letoff adjustments for the escapement.  The escapement
lets go when it feels like it, or perhaps when the hammer actually
hits the strings.  There is no repetition assistance, so the key
must be released back to rest position before restriking the note.
Nevertheless this action is so light and quick that it is said to
be the best for playing music where grace and agility are more
important than powerful sound.

Of course a 1906 Boesendorfer grand may have all the sound power
that Beethoven could wish for, and the action may have been
improved (with more adjustments and capabilities) since its
invention by Stein in Mozart's day.  Anyway, I'd love to hear
the facts.

Thanks, Mike Knudsen