I knew when I read Gary's question that Matthew would have a good
response.  Both his and Adam's responses are right on the mark and 
I have little to add to them.  From the perspective of a musician 
and a frustrated but glad arranger, I thought that perhaps ease of
arrangement is being overlooked as a factor in tune choice.

Particularly in later years, as the arrangements of Wurlitzer and its
successors grew arguably less artistic and more workmanlike, I cannot
imagine that much effort was put into finding ways to arrange tunes
that were difficult to fit into the non-chromatic band organ scales.
Even during Wurlitzer's best years, I think that music written in
certain keys and not easily transposable might have been summarily
rejected.  Wurlitzer's arrangers were excellent but not miracle
workers!  It would be interesting to consider how much of the
difference between Wurlitzer's 165 and the relatively congruous 125 
and 150 scales might be ascribed to the inclusion on 165 rolls of tunes
that might have been too difficult to arrange for the other two more
limited scales.

One last thought: I feel that popular music today, if you can call it
that, is unquestionably more lyrics-based than music-based.  Somewhat
unsurprisingly, then, I find that many of the tunes from the past 
which are best remembered today have excellent lyrics and perhaps 
less compelling music.  I think "Makin' Whoopee" and "Button Up Your
Overcoat," which have both been mentioned, would both fall into this
category.  Fine tunes they are indeed, but I find these songs
appreciably less interesting without the lyrics.  Assuming that we
accept this premise, would Wurlitzer have included these tunes because
they were popular or left them out because they made for less
interesting musical arrangements?

TJ Fisher
Washington & Lee University [Sigma Phi Sigma] '15
Lexington, VA