Hello!  Re "Photogrammetry and PostScript for Roll Readers"
[Julie Porter, MMD 000928].

One of the top organ/orchestrion/player piano rebuilders (in my
opinion) here in Germany built a machine of this sort more than 10
years ago.  It uses a one-row CCD (charge-coupled device, like those
used in copiers) and a camera optics placed about 60 cm above the
moving roll.  The roll runs on a black background (rubber cloth!) so
that the holes are "seen" by the CCD at a very high contrast.

The scanned data are fed "as-is" into a computer (in some serial pixel
format) and saved.  An analysis program later reads these data, is told
about where the tracks are and writes a MIDI file containing the notes.
(As far as I know, the MIDI file also contains the information about
"non-note tracks" like pedal or tracking holes for certain very special
roles -- all that is reproduced on the corresponding punching machine).

The whole scanning machine looks like a joke when you see it for the
first time: a quickly-assembled structure of various aluminum profiles,
dangling cables, without diagonal reinforcing, looking quite shaky.
Actually, it is a quite sophisticated machine that has served its owner
for a long time.

Harald M. Mueller