The easiest way for Brian Walter to get his own selection of tunes
arranged for a small organ is to talk to his roll supplier.  He
mentions Melvyn Wright, who will be willing to arrange any suitable
tune.  Brian may even be lucky enough to choose a tune with a wider
interest than just his own, so the cost may be not much more than a
standard roll.

Arrangers are always looking to increase their roll selection and are
open to suggestions from customers.  Of course, if the tune is not
suitable for the scale, any good arranger will politely refuse the job.
A poor arranger, however, may try, but with suspect results.

Unless you are a good musician with experience in arranging music for
small scales, do not try to rearrange MIDI files downloaded from the
net.  Even good arrangers can take longer doing it this way, rather
than working directly onto paper or using an arranging program.

Nicholas Simons