I am trying to discover the function of a special code perforation that
occurs on Duo-Art piano rolls specifically made for concerto
performance.  The rolls contain all the normal Duo-Art codes, but two
holes in the tracker bar control additional functions.

Often the piano is at rest while the orchestra plays.  In these cases,
the roll is stopped until the piano part resumes.  Both Ampico and Duo-
Art accomplish the "rest" or pause mode with a REROLL perforation.  In
the case of the Duo-Art, the reroll perforation throws the transmission
into neutral.  This is easily done on most Duo-Arts by tubing both the
reroll and repeat valves to the tracker bar REROLL port on the extreme
left side.  When the conductor wants the piano to resume playing, he
pushes a button that disables the reroll valve.  Since the reroll
tracker hole is still open, the repeat valve immediately engages the
transmission again, and play resumes without delay.

Concerto rolls may have numerous reroll perforations throughout the
roll.  Thus, playing these rolls on an unmodified piano gives poor
results unless the reroll function is disabled.

But my post today doesn't concern the pause function, since many of us
clearly understand it and have used it successfully in concerts.  My
question concerns the other special perforations that I find on the
concerto roll set of the Tchaikowsky Op. 23, No. 1 played by Grainger.
On the extreme right side of the Duo-Art tracker bar, is the soft pedal
perforation.  Next to it is the mostly unused "motor off after rewind"
hole.  On this roll set, perforations occur frequently in this
position.  Most of the time the perforations occur simultaneously with
snakebites.  Most of the time these perforations occur when theme level
15 is set.  They also occur at theme level 12, but only when level 15
has been used in close proximity.  But there are times when theme level
15 is set and these perforations do not appear.

Has anyone figured this out?  I'll continue to analyze this, but so
far, my only conclusion is these perforations occur only when the
loudest playing is desired.

Bob Taylor
Missouri