Welcome, Bruce, to the frustrating world of the Residence Player Organ.
On your calendar, pencil in the next ten years of your life!  Could you
share with us the original Opus number, so we could look up the date
and history of the instrument.  If the nameplate is missing, the four
digit Opus number is stamped or scribed on the lowest pipe of every
rank.

> It came with the original electro-pneumatic switching unit and a newer
> 1970's vintage solid state switching unit.  Are there any thoughts as
> to which one I should use or should I get rid of both of them in favor
> of one of the new computerized systems that lets me play the organ
> using MIDI files?  The original unit is quite a piece of craftsmanship
> and even has glass windows so you can watch it operating.

The glass fronted boxes are the toggle units for the Duo-Art system.
On Duo-Art rolls, the stops and other functions are turned on and off
with the same perforation; the first punch turns the stop on, and the
next punch turns it off, and so on.

The old solid state switches probably replaced Aeolian's elaborate and
difficult to maintain electro-pneumatic couplers and switches.  But
they would likely be unable to perform the toggle action I described.
So if you retained the old switches, you would also have to keep and
use the Duo-Art electro-pneumatic toggle chests.

A new generation computerized switching system could replace
everything, providing one could add some custom programming to achieve
the Duo-Art toggle action.

> Has Larry Broadmoore invented a PowerRoll for Duo-Art Organs?

Possibly, but not likely.  He would have to invest in retooling for
virtually every part, to accommodate 176 staggered holes at 1/12"
spacing.  But such a thing is unnecessary.  The real-world parallel
outputs from the MIDI converter (Octet or whatever) can be fed through
diodes directly to the organ's electrical inputs.

> My second question has more to do with aesthetics and tonal structure.
> I like the theatre organ sound just as much as I like the classical
> organ sound so I'm considering adding a rosewood xylophone and a few
> ranks of theatre organ pipes.  Most organ builders cringe at the
> thought of this.  (Keep in mind that most organ builders consider
> theater organs totally bereft of any musical value).

Personally, I don't; I think that is a fine idea.  Some residence
organs have been justly criticized for rather dulcet, wimpy voicing and
tonal design.  Rather like the studio pipe organs that used to
accompany radio soap operas, back when there was such a thing as live
radio.

You should correspond with Paul Morris (see 010527 MMDigest).  I heard
his organ in person, and believe me, it is awesome.  Through careful
voicing, his stops have a brilliance, presence, and differentiation
between voices that far exceeds the average RO standard.

As a fine organist and pianist as well as a mechanical music fan, he is
master of both the classical and the popular repertory.  Paul can make
his instrument sound as 'nice' or as 'nasty' as the music requires.  So
I feel sure that he would be sympathetic with your desire to modernize
the tonal design of your organ.

Richard Vance