In the New York Times online Classical Music Web Forum there seems to be
a parallel thread on the subject of soloists memorizing music they are to
perform.  One of interest is from the eminent Canadian pianist, Jon Kimura
Parker, posted three days ago.  His contribution:

   "I have spent an hour this morning ensuring that the opening
   movement of Mozart's Sonata in A Major K. 331 is thoroughly memorized
   for tonight's recital, and I am quite sure that this process will in
   no way improve my performance. And while my memory has always been
   excellent, I have often found the pressure of memory to be distracting
   from other, more musical concerns.

   I concede that a concert is indeed a high wire act in some respects.
   Perhaps memorizing a work will not enhance my own performance, but
   will in fact enhance a concert-goer's perceived experience.  This is
   also an important question.

   Nonetheless, I am looking forward to the next few weeks of concerts
   primarily because they are all of chamber music, and I can finally
   relax and just make music." -Jon Kimura Parker

Scott Morrison