(A close encounter with a tracking system of the third kind!)  Before we
get away from tracking systems, I would like to run this by the folks
reading MMD.

Years ago, 25 or 30, I came across a player having a tracking system
having a roller -- maybe two of them, above or below the tracker bar and
the length of the tracker bar -- that would push the roll slightly
further from the tracker bar on one end or the other in response to being
too far to the right or left, instead of laterally shifting the roll or
the tracker bar.  Seems like the roller was maybe a quarter to
five-eighths inch in diameter.

The operating principle seems to be that since roll frame misalignment
will cause a roll to creep to one side, then a variable roll frame
alignment device can be used as a tracking system.  I just saw the thing
briefly somewhere, didn't take notes or pictures or anything, and can't
even remember now if it was a player piano or an orchestrion of some kind.
I seems like it wasn't a U.S.-made machine.

Does anybody know anything about this type of tracking system?

Dick Merchant
Carlsbad, NM

 [ The printing industry surely experimented with all sorts of devices
 [ to control the tracking of the paper 'web' as it moves through the
 [ banks of a large high-speed printing machine.  Perhaps this is one
 [ of those devices.  -- Robbie