I have written several times about the "O" roll and Coinola piano that
plays this style of roll.  Many of the homemade machines built in the
1970s utilized the "O" roll with the result that some sounded good and
others not so great.

The distance and length of percussion holes varies between tune one
and tune ten.  The tracker scale has been published many times and
there are at least two variations of the tracker scale published over
the years.  The scales in the Reblitz books are generally considered
correct.

A. The first large hole is the play hole that tells the machine
   to put the transmission in the play position.
1. Tympani
2. Bass Drum and cymbal
3. Tympani
4. Wood Block
5. Snare drum single tap
6. Snare drum reiterating
7. Triangle
8. Sustain Pedal
9. Hammer rail rest
10. Hammer rail soft position
11. Mandolin off
12. Mandolin on
13. Pipes or reeds on
14. Bells or Xylophone on
15. Low vacuum to percussion (usually the snare drum)
16. Normal vacuum
17. Bells or Xylophone off
18. Coin trip (off)
19. Pipes off

20 to 31: e to d# octave coupled to lowest bass notes
32 to 85: E to A

86. Tambourine
87. Amplifier of pump to increase overall vacuum
88. Crash cymbal (only in Coinola SO)
B. Rewind

Early Coinolas have a little pneumatic, controlled by holes 15 and 16,
to move the tympani beaters closer to the drum head for a soft effect.
Later Coinolas did not have this feature so holes 15 and 16 controlled
only the snare drum loudness.  The Crash cymbal, controlled by hole 88,
is usually only found in the SO housed in its own box.  I think it may
have been a Chinese cymbal.  The SO has swell shutters that are thought
to have been controlled by the pipes on and off or it may have been
controlled by the pump amplifier.  I do not know for sure.

Machines with two ranks of pipes and no xylophone or bells have the
violin pipes controlled by 14 and 17.  The drums play softly in an
original Coinola and do not stand out like a band organ drum.  The
bells in original Coinolas do not play as loud as many homemade
Coinolas.

The original rolls have control perforations punched for loud and soft,
as if they are controlling the piano vacuum, so you may add that control
your homemade "O" roll piano.  Original instruments that I have seen do
not have this feature.

Personally I find the music of an "O" roll very good.  Most arrangements
are very enjoyable and musically pleasing to me.  I also enjoy Wurlitzer
music and "A" rolls, while others enjoy the "G" roll.  If I were going
to build an orchestrion that is homemade and not a copy of any particular
original machine then I would lean toward building a G-roll piano.

The problem with me (one of many problems) is that I would want to make
my homemade machine as close as possible to an original.  Many of today's
builders just do not have access to an original machine to copy and I
would think that if you are contemplating the building of a nickelodeon
that you would ask questions to the MMD.

Don Teach
Shreveport Music Co.
Shreveport, Louisiana