Ben Gottfried said "Andy Struble has asked for a source of MIDI music
files for his 97-key Mortier organ. ... Tom Meijer ... will need to
know the exact layout of the organ, of course, as there are so many
variations.  I think it is said that Mortier made all the organs
differently with respect to functions of the keys so that the owners
could not exchange books and keep his book sales proprietary."

I think Ben's comments reflect a cardboard book perspective, and from
that viewpoint I would agree.  With regard to variations in book scale
or tracker bar/keyframe variations between essentially the same organ
scale, the same thing has been introduced when organs are MIDIfied by
different technicians.  In reality, the "Ames Scale" has a number of
variations.

Adding MIDI to organs opens up the possibility of doing things in
software which required a greater depth of effort and/or knowledge
when dealing with books and rolls.

I assume that Andy may have meant "more music for our organ," not
necessarily "new arrangements," and that some of his needs might be
met by adapting existing MIDI files.

Of course creating a MIDI arrangement requires musical skill, but
moving an existing MIDI arrangement can sometimes be successfully
reduced mostly to creating an "patchboard" to reroute the MIDI file
notes to other "wires."  It then becomes a mechanic's task rather
than a musician's task.

I made a presentation on arranging at the COAA/AMICA Princeton
gathering last fall in which I outlined how the MIDI File Mapper
program can be used to do this.  I have some notes available at

http://www.wallace-venable.name/mechanical-music/Princeton-Arranging/MIDI%20File%20Mapper%20-%20Preliminary%20Notes.html 

Wallace Venable