I heard a recording of Bach's Mass in B minor on the Archiv Production
label.  The liner notes said the mass was performed on period instruments.
I automatically knew the mass was going to sound like it was in B-flat
minor instead of B minor.  I went to my digital piano and played along with
the Kyrie in B-flat minor, then I tuned my digital to A415 and played in
the correct key, consciously transposing as I went along.  When I played
with the performance in B-flat minor, at A440, it was perfectly in tune.
It seems like music was a half-step lower 250+ years ago!  When did A440
became the standard? I'm sure if Bach and Handel came out of their grave
today, everything would sound sharp to them.  If they heard Bb, they would
hear it as an A.  They would have to recalibrate their ear and give the
pitches in their heads new names!

Jeremey