I already have a couple of opinions, but thought I could get a few more
from the MMD members.

As everyone who owns a Duo-Art knows, the expression level holes on the
tracker bar are located above the row of note holes.  This was done to
allow the piano to play either all 88 notes (on earlier 88-note-stack
pianos) or to play 80 notes with bass and treble vacuum level control
in the Duo-Art mode.

The altered position of the expression holes means that for an expres-
sion valve and a note valve to be opened simultaneously, the expression
hole has to occur later on the roll than the note hole.  The rolls were
coded with this in mind.

If a device, such as the Power Roll tracker bar interface, is used
to play the piano in the place of a roll, does there have to be any
modification to the roll image in order to preserve this timing
relationship?

The Power Roll (or other electrically controlled valve bank) will hook
up to all of the tracker bar ports as if they were in a straight line
(with respect to time).  Would this have the effect of actuating the
notes sooner than their associated expression codes?  Does there need
to be a delay introduced so that they will line up properly?

Spencer Chase

 [ You're right: the wireline signals sent to the PowerRoll just turn
 [ on and off the magnet valves, and so _spatial_ correction is applied
 [ to the perforator-control data file in the same manner that the
 [ offset holes in the Duo-Art tracker bar match the displacements
 [ punched in the music roll.  The CD-ROM files offered by Wayne Stahnke
 [ provide the proper spatial corrections to the scanned roll data.
 [ -- Robbie