John Tuttle's little observation (if that's the right word for hearing,
not sight) is very interesting.  I've noticed something like this with
the resonance in a large church, when the organ has finished playing
a "tutti" chord at the end of a piece.  However, instead of the pitch
rising with the fading sound, it drops slightly!

This only seems to happen when I'm actually listening in the church,
but not on a recording when I'm sitting in my living room.

Regards,
John Page