While it is true that for General MIDI files (that play on computer
sound cards and synthesizers) the percussion channel is 10, that has
almost nothing to do with MIDI files used to play MIDI-fied band organs
and such.  General MIDI was invented so that people creating MIDI files
would hear the same results no matter whose sound card was used for
playback.  Within channel 10, notes were assigned to various percussion
instruments, bass drum, snare drum, cymbals, etc.  One glaring mistake
was that there is no snare drum roll in General MIDI (although Yamaha
added one for their XG system).

MIDI files to play MIDI-fied band organs and orchestrions have three
sources: 1) create from scratch, 2) convert from digitized band organ
or orchestrion rolls, or 3) convert from random files from the Internet.
I have never tried to create a MIDI file from scratch, since I am no
musician.  I have converted a few files from the Internet, but this is
often not very satisfactory simply because these files do not fit the
target instrument very well.  I have done a great deal of conversion of
digitized rolls from one format to another and the success of this is
determined by how well the original instrument matches the destination.
Taking a digitized O-roll and converting it to play on a Wurlitzer 125
is probably not going to work very well musically.

The question of which channel to use for percussion comes down to the
interface you use to run your instrument.  If it is small, needs only
one MIDI driver for all the notes and percussions, and the MIDI outputs
are not programmable, then the percussions must end up on the same
Channel as the notes (often Channel 1).  This does not mean that the
MIDI file needs to have all the notes and percussions on the same
Track.  It is much better for purposes of editing if the musical parts
(bass, accompaniment, melody, countermelody) are on separate tracks
with all tracks having the same channel number.  Notice that this means
the file must be a type 1 MIDI file.  I would go farther and say that
the individual percussion "notes" be put on separate tracks, again, for
ease of editing.  This might mean bass drum on track 5, snare on track
6, triangle on track 7, etc.  Again, all of these tracks would have the
same Channel number.

Another trick is to make the note velocities of the percussion "notes"
a very small number, perhaps 2, 3, 4, 5.  Any note velocity greater
than 0 will cause the MIDI board output to turn on, but if the file is
auditioned through your computer sound card, the percussion "notes"
will not be heard even if they are played on the same channel as the
playing notes.

I am always interested in communicating with people who have MIDI-fied
instruments of any type.  Let me know what you are trying to do and
perhaps I can be of assistance.  I would also like to encourage anyone
who has the inclination to create new MIDI files for old instruments
(S.K. Goodman being one of them) to keep up the good work.

Craig Williams
Scotts Valley, California