Kevin McElhone states that he has a Wilcox White organ combination
pushup with three controls at front, one is missing.  Those he has are

  Tempo -- speeds marked largo, presto, etc.
  Loudness -- from pp to ff.

My machine also has a Sustain lever on the front apron: a lever that
moves left-right.  Not that I want to discourage you from writing
another book.  The ones I already have are great.

Regards
Craig Smith