Hello, Chris,  I think you should start by deciding what band organ
sound you like and then choosing a roll/book/MIDI scale from there.
Once you make that choice, you can tweak the sound of your home-built
organ, within certain limits, by your choice of pipe ranks and
percussion.  For my personal taste, the Wurlitzer 165 is the scale of
choice.  You indicate that you are leaning in that direction yourself,
but you prefer more trumpets and bells.

Are you aware that the 165 scale has provision for more bells and
trumpets (including brass) in its register controls than the 165 organ
was ever equipped with?  The larger 165-playing organs, few or none of
which survive, had these additional ranks and bells.  One of the
benefits of the 165 scale is its ample provision of automatic register
controls to turn on and off more ranks and percussion than most other
organs had, including swell shutters to further vary the organ's sound.

You certainly need to take into consideration the availability of music
for whatever organ you build.  You are in Europe, and it might be a bit
unhandy and expensive to ship 165 rolls from here to you.  But if you
made your organ MIDI controlled, you would solve that problem, since
very extensive MIDI files of 165 music are available.  One of your
problems is going to be procuring a reliable roll frame, and if you opt
for exclusively MIDI operation, you eliminate that problem -- but also
the pleasure of watching the roll pass over the tracker bar to play the
organ.  My choice would be to have dual control, MIDI and paper.

Doyle L. Lane's paperback book, "Wurlitzer Band Organ Pipe Scales,
Copied From The Original Wurlitzer Pipe Room Scale Boards", gives
dimensions for many of the pipe ranks in the Wurlitzer 165 organ.  The
specifications are not complete however, being only what Doyle was able
to copy from partially-rotted pipe-scale boards found in the basement
of the T.R.T. shop, when he bought the business from Ralph Tussing's
son, Gordon.  The critical dimension lacking (but estimatable by one
with musical talent) is pipe length.

Belgian organ builder Johnny Verbeeck has the complete set of pipe
specifications for all sixteen ranks of the 165 organ, but of course he
treats that as information of value and does not give it away.

If you go to the Sounds page of my web site, you will be able to listen
to about 60 tunes played on various Wurlitzer 165 band organs.  If you
like them, the 165 scale is the way to go:  http://wurlitzer-rolls.com/ 

Matthew Caulfield
Irondequoit, New York