Hello MMD.  In the recent discussion about binary storage and
time resolution, the question was raised, "Could a wide piano roll
perforation be made to signify something different from a narrow
perforation?"

I'm surprised that no-one mentioned the Solo Carola system, because
it uses wide perforations for accented notes and narrow ones for
accompaniment notes.  The tracker bar has an extra set of thin vertical
slits in it, above the normal tracker bar holes.  These slits are
situated so that they are uncovered by wide perforations but not by
narrow ones.

The Solo Carola hammer rest rail is split into 44 separate sections
each controlled by its own pneumatic.  Normally the pneumatic holds
its section of rest rail in the half-blow position, but if a wide
perforation is detected by its thin tracker bar slit, the pneumatic
collapses to the full-blow position, ensuring an accented note when the
perforation reaches the normal tracker bar hole.  This arrangement means
that adjacent semitones, if played together, must always both be loud
or soft, but it would be very rare for this to be a problem.

Solo Carola rolls have an extension on the left-hand spool end which
pushes the left-hand spool chuck further to the left than normal and
this engages the rest rail mechanism.  For ordinary rolls the player
behaves like any other 88-note foot impelled player.

John Philips in Hobart, Tasmania.