I have two Duo-Art transposing tracker bars, one in use and a second
kicking around in my parts somewhere.  They move only the 84 note holes
in a strip in the center of the tracker bar, making them perfect if you
have a piano with an 88-note stack and you want to pull those bottom
four notes up into the pianos playing notes.

Frankly, I love it and wouldn't want to live with out it.  Everything
sounds different (of course) and the sound of those bottom four notes
is wonderful, whether playing Liszt or Milne.  If you want my spare
tracker bar, let's talk, particularly if you have an electric motor
from a long-play Duo-Art top action...!

Bruce Grimes