In discussing the Golden Gate Park Carousel Organ, San Francisco,
(MMD 010105) Julie Porter wrote:

> What is the actual scale of the Style 107?  The instrument in Golden
> Gate Park was playing Wurlitzer 150 rolls.  If there was more bass
> notes in the original organ, would not Wurlitzer 125 rolls give
> better music?

The Bruder Style 107 scale contains five bass notes.  However, other
factors need to be taken into account when converting an organ from one
scale to another.  Unless major alteration to the pipework is to be
undertaken, it will be necessary to ensure that the pipework for the
accompaniment, counter melody and melody sections will also accommodate
the new scale.  Additionally, for the most musical results, the
relative tonal balance of these sections in the original organ will
need to be compatible with those typically encountered on organs
playing the new scale.

My understanding is that the main melodic line of a Wurlitzer 125 is
made up of trumpet and piccolo pipes, with the piccolos carrying on up
the musical scale from the top of the trumpets.  The Bruder 107 has
fourteen trumpets for the counter melody section.  However, the top
seven of these use the same tracker bar holes as the melody pipes.  An
additional tracker bar hole is used to disconnect the trumpets to allow
the melody section to play solo when required.

The melody section of the Bruder will generally be made up of violin
pipes as a foundation tone with a mutated mixture being brought into
play with the 'forte' register.  The melody section contains 22 notes,
although as already stated, the lowest seven are shared with the
counter melody.

As should be clear, the balance between the trumpet/piccolo combination
in the Wurlitzer 125 will be quite different to the trumpet/violin in
the Bruder 107.  In the Wurlitzer, the trumpets will be a dominant
foundation tone carrying the melody line augmented by the piccolos.
This is not the case in the Bruder where the trumpets will not be
voiced so dominantly.  If the music for the Wurlitzer 150 is arranged
with the 'melody' section being musically dominant, rather than a
'trumpet' section, it is likely that it would be more suited to the
tonal balance of the Bruder organ.

The overlap between melody and counter melody in the Bruder scale may
also not be compatible with the break point between trumpet and piccolo
on the Wurlitzer.  Not being familiar with the Wurlitzer 125 scale I am
not able to elaborate further on this point.  Depending on the method
of register control used on the overlapping trumpets and melody notes
on the Bruder, it may not be possible to obtain separate operation of
these pipes (if necessary for the new scale) without separating them on
the main wind chest.  This would cause additional work.

> The roll reader seems like it would be reversible.  It does not look
> like there was anything done to the pipework.  I am not exactly sure
> how a keyless system works.  Is that the one with a star wheel?

I do not know what you mean by 'the one with a star wheel'.  Book
operated organs using a 'keyed' system use a row of small levers to
read the music.  The only use of star wheels to read music that I can
recall is in disc musical boxes.

In book operated keyless organs, as the music passes over the tracker
bar the perforations allow air to escape from the system.  The
resulting drop in pressure (the organ mechanism works with air at above
atmospheric pressure) is used to operate the mechanism of the organ.
The music is held firmly against the tracker bar by means of rollers.

I suppose that it would be possible to connect a book keyless mechanism
to a paper roll mechanism, but it would be necessary to ensure that the
paper is held firmly against the tracker bar.  Some paper roll organs,
which do not employ a vacuum operated roll reader, also use a roller to
hold the paper against the tracker bar.

As with all conversions, the reversibility of the addition of a roll
reader would depend on how it was installed.  Hopefully it did not
involve the removal or alteration of any of the original mechanism and
only consisted of alteration to the pneumatic tubing to connect the
original organ to the new unit.

Regards,

Douglas Bush
UK