The Wurlitzer 150 band organ scale is written as if the organ were in
the key of C.  The 150 organ actually plays one whole step lower, so
each note marked C in the scale actually sounds Bb.

This is similar to the hand-played Bb clarinet and trumpet, which play
notes a whole step lower than the notes written on the music
manuscript.

Art Reblitz
www.reblitzrestorations.com