String Levelling guestions

[A440A]

Gina writes:

<< it seems to me that the force of the hammer repeatedly hitting the
string in varying degrees (from pp to fff) could cause the strings to alter
planes.>>

    Greetings all, 
       IMHO< what it does is alter their phase.  The individual strings may
vibrate at exactly the same speed, but the uneven impetus that results from
"unlevel" strings causes one or more of the strings vary in amplitude.  Since
all three strings are coupled at the bridge, this translates into a energy
transfer situation, with strings giving and taking acoustic energy from one
another, attempting to resolve on one point.  There are energy/impedance
values that oscillate back and forth between coupled strings vibrating at
varying amplitudes.  
     This behaviour is observed,(though not aurally),  with coupled
pendulums,(via a torsion bar,etc).   You can set one in motion, and
immediatedly, the second begins to move, always increasing amplitude while
attempting to catch up with the first. The first will begin slowing down,
until the two reverse their original starting.  The first pendulum will be
motionless for a  about half a cycle, while the second one makes its widest
trip.  So the "motion" goes back and forth, from one to the other. 
    When piano wires do that, you can hear it as a long whine in the
aftersound,  my logic says this results from a changing of speeds, as the two
or three strings attempt to find each other.  
    Weinreich writes more thorougly of this effect. 

Regards,
Ed Foote 
Precision Piano Works
http://www.airtime.co.uk/forte/history/edfoote.html