In case anyone missed it, it's important to stress that the Wurlitzer
125 scale can use the trumpets as an independent countermelody, as a
traditional European arranger or any good current arranger would do.
I've heard that one reason the stock Wurlitzer 125 arrangements are
so dull is that the organs might be poorly maintained at the county
amusement park, with some trumpet notes weak or dead, and likewise
the melody chest might have a few dud notes. But with both sections
playing the same notes, each would fill in for the other's gaps.
Just speculating, I would say that somewhere above a 40-note scale
is the right place to add a countermelody section, at the expense of
some melody notes. From experience with the Raffin 31er scale, I would
say that you need in the high 30s of notes to do justice to bass,
accompaniment and melody before considering a countermelody section.
If the CM and Mel sections are adjacent in notes and have some
registers in common (say, bourdons and cellos/violins), they can be
used together as an extended melody section, thus relieving the need
for a full 1.5 to two octaves of melody scale.
I agree, the Wurlitzer 150 scale is terribly deficient with only three
bass notes, duplicated in the trombones. But I understand that bass
notes would be played legato in the bourdon basses and staccato in the
trombones, thus giving a plucked effect. I'd say an organ needs at
least six, if not seven, bass notes. Big Stinson organs have eight
bass notes, and David Wasson's "Trudy" has all twelve.
To add the to confusion re "contra", I believe that "contra (or contre-)
dancing" is a corruption of "country dancing," as in Morris, etc.
Just my two cents