Just a reminder that I wrote about this system on the Digest some
months ago.  ["Philipps Ducanola Roll Tracking System" in 001114
MMDigest]

Not that uncommon in the UK, it was covered by two British Aeolian
patents and is found in two forms: one with fixed tracker bar (and
a reroll centering device) and bleeds into the motor pneumatics, and
one with a floating bar (no reroll centering needed) and primary valves.
The left hand slots are connected (logical 'or' function), ditto the
right hand slots.  The regular disposition of the vertical slots
serendipitously ensures adequate tracking inputs on most music...

Unless the motor bleeds are just right, the first type is too sensitive
to 'number of tracker slots open', and is often found disabled with
ears substituted, though Malcom Cole has a fine Steinway O of about
1914(?) in which it works fine.  The later system is number insensitive
and works well.  Aeolian also seem to have used up spare bars later on
players where the vertical slots were never tubed up and tracking ears
were used.

The apotheosis of tracking systems is the British Aeolian (Nicholson)
4-hole system, which does _not_ work like the Standard and other systems:
it is not designed primarily to cope with narrow(er) roles, but by
cunning pneumatic logic to cope with torn edges.  It has a floating
bar, no ears to eat paper, requires no reroll centering system -- and
it works superbly when adjusted correctly.

If anyone's particularly interested I can find the patent abstracts
with descriptions and drawings for all three.

Paddy Handscombe
Wivenhoe, Essex, UK

 [ Would you please do so, Paddy?  I'd like to enlarge the MMD Tech
 [ 'library' with articles and illustrations of the various music roll
 [ tracking systems.  (In fairness to other music roll formats I should
 [ note that a music roll centering device is generally needed only
 [ with the "American piano roll" format, with its crude concave
 [ flanges.)  -- Robbie