After searching the vast and valuable MMD archives, I have found rather
little information about the B.A.B. 87-key scale.  However, after
listening to recordings of the Ruth organ at the Spokane carousel
(which plays said scale), I realized that the Ruth must have been using
what I can only assume is register control for what sounded like quite
a few ranks of pipes. My theory, is that the B.A.B. 87 key scale has
close to the same range of the 66-key scale, but has more holes in the
tracker bar for registers. I may be completely off with this theory, so
if anyone can correct me, please do so.

Will Eley

  [ According to "Treasures Of Mechanical Music," by Art Reblitz and
  [ Dave Bowers, the B.A.B. 87-key scale has eight register controls
  [ for the various pipe registers, while the B.A.B. 66-key scale has
  [ six such controls.
  [ --Relief Editor.