Yesterday Mr. Herr asked if it would be possible to convert an
Orchestrelle to play 88-note rolls.  The answer is maybe, depending not
on the model, but the age of the instrument.

The difficulty is that 58-note rolls had very large perforations
(0.105"), and proportionally large bleeds.  Modern piano rolls, with
their small perforations, won't respond at all, unless the bleed size
is reduced.

Prior to about 1906, Orchestrelles were single valve, with the tracker
bar connected directly through channeled boards, to big 1-3/4" pouches
and really big bleeds.  It is unlikely that these big pouches, and the
big, heavy playing valves could be made sufficiently quick acting and
responsive, even if the bleeds were made much smaller.

Later models of 58-note instruments (and all the 116-note instruments;
F, XW, XY) were double valve, with small, 7/8" primaries.  You can tell
if your instrument is one of these by the fact that they were done with
tubing, rather than channeled wooden boards.  Such instruments could be
converted, providing the bleeds were reduced in size, on 58-note
models.  But this would have to be carefully done: you are working with
less than 3 inches WC wind pressure.  116-note models already have small
bleeds, to operate with the tiny holes in a 116-note roll.

In either case, you can do an experiment to see if the project is worth
pursuing.  Slit a piano roll to 10-1/8" wide and wind it on an organ
roll spool.  It won't make music, but it may cause the system to
respond, providing you fix the bleeds.

The easiest way to do this, in a reversible manner, is to cover the
array of green celluloid disk bleeds with sticky paper (removable Avery
folder labels), not tape.  Orchestrelles, using pressurized spool box
logic, have the bleeds outside, venting to atmosphere.  Using a thin
needle, poke tiny bleed holes in the paper, over the existing holes.

Assuming your instrument is 58-note, the single valve models have the
bleeds directly in front of the pouches, at the lower rear of the swell
chest; reasonably accessible without too much disassembly.

On double valve models, you can see the bleeds, if you look straight
down between the back of the spoolbox and the primary valve chest, with
a flashlight.  But you can't get to them, unless you open the primary
valve chest, and then carefully remove the lower part of the primary
valve assembly, leaving the pouch board and bleeds accessible.

Richard Vance