The digest of 95.06.06 has several references to CCD scanning of piano rolls.
A few years ago I was doodling with this concept.  There are single line
diode arrays of the type used in hand scanners.  Figuring our suitable optics
stumped me on that one.  Maybe you could run fiber optics from a tracker to
the array face.  The other approach was trying to figure out how to get a
single scan line from a CCD video camera.  That interested me because I
actually had the notion of lining up 88 people with football stadium
black/white flip cards and...  oh well, no one is going to believe that one!

MIDI to Pianocorder:  The Pianocorder system has high voltages and most of it
is not isolated.  The simple solution to protecting yourself (and your
computer) is to put a optoisolator between the two.  Actually, you have to do
this anyway because the Pianocorder wants to see a 12 V signal.  I have used
a Sharp PC900 because they were handy (it is pretty much the standard device
used in MIDI interfaces), but most anything will do.  If anyone is
interested, e-mail me your real address and I will send a schematic along
with a couple of PC900s.

I speak with experience on the above.  My first prototype MC-1 MIDI to
Pianocorder box did use optoisolators, but "cleverly" stole +5V from the
Pianocorder.  My first prototype also blew up the Mac MIDI interface of my
first customer.

Will Dahlgren