Tunes found on O rolls, G rolls, H rolls, M rolls, A rolls and others
were originally converted from the source 88-note player piano rolls,
not from each other, because each style of coin piano and orchestrion
roll has a different number of playing notes, octave-coupled bass notes
and treble solo notes:

A rolls
  58 playing notes C-A
  Coupled notes vary depending on brand and model of piano
  No treble solo notes

G rolls
  48 playing notes G#-G
  12 coupled bass notes G#-G (10 in keyboardless pianos)
  No treble solo notes

H rolls
  66 playing notes E through A
  10 coupled bass notes G-E
  34 treble solo notes C-A for pipes
     Violins and flutes play an octave lower than associated piano notes
     Piccolos and harmonic flutes play the same pitch as assoc. piano notes
  22 treble solo notes C-A for xylophone

M rolls
  64 playing notes A through C
  No coupled bass notes
  27 or 32 treble solo notes for violin and flute
  19 treble solo notes for xylophone, bells or piccolo

O rolls
  66 playing notes E through A
  10 coupled bass notes E through A (fewer in some models)
  24 treble solo notes A#-A

Ideally, the conversion process for each type of orchestrion roll
involves these steps (not that every step was always followed
meticulously):

1. Truncate the 88-note version to the shorter musical note scale
of the orchestrion roll, filling in the missing bass and treble notes
in a musical way without making the arrangement sound muddy.

2. Alter the bass and accompaniment notes to accommodate the octave
coupler.  If more than one bass note is played at the same time in
the octave coupled range, it will play chords, usually an undesirable
effect.

3. Alter the tenor countermelody parts so the tenor notes don't play
on the bass octave coupler.  This takes the most creativity in G rolls,
in which the bass is coupled all the way up to G below middle C,
leaving very few tenor notes to carry countermelodies.  In that case,
many of the tenor countermelody notes must be moved up into the octave
above middle C.  Simultaneously, the accompaniment chords must be
inverted if necessary so they neither encroach on the bass octave
coupling nor duplicate important tenor countermelody notes that have
been displaced.

4. In an orchestrion with a treble solo section, completely rearrange
the music in that section to accommodate occasional solos and duets.

Once an 88-note arrangement has been modified to fit a certain
orchestrion scale, it is more work to undo and redo the octave
coupling, recreate the lost countermelodies, and rearrange the solo
parts than it is to start over from the piano roll.  Converting from
one style of orchestrion roll to another isn't impossible, but more
of the original 88-note artist's arrangement will be lost.

P. M. Keast -- arranger and orchestrator for the coin operated division
of QRS, then Clark Orchestra Rolls, and finally the Capitol roll
division of Operators Piano Co. -- said QRS had machines that could
read 88-note piano roll masters and be set to print out orchestrion
masters with the notes in the correct positions for each type of coin
piano or orchestrion roll.  Those printed orchestrion masters would
then be taken by the coin-op arranging staff and modified separately
for each scale.  The different results are very obvious if you compare
the percussion and expression on two types of orchestrion rolls taken
from the same 88-note master (such as G and H rolls), let alone the
note-field arrangements.

In the original era, there was no attempt to automate the conversion
process beyond transcribing the basic note arrangements ready for
editing, because in each case it takes a skilled musician to arrange
musical sounding treble solos, appropriate bass octave coupling, and
rearranged countermelodies and accompaniment chords.  Attempts in
modern times to transcribe mechanically from one style of roll to
another, without intervention by a human editor, have resulted in some
poorly arranged conversion rolls (just as MIDI arrangements for one
type of orchestrion or organ frequently sound unmusical when played on
a different type of instrument).

Art Reblitz
Colorado Springs, Colorado
http://www.reblitzrestorations.com/