Gidday, Bill -- Greetings from across the Tasman!  I have just
completed a 16-note brass whistle calliope which I run from a MIDI
programme through a laptop, so may be able to help.  I have a steam
background, having made 3-1/2 inch and 5-inch locomotives and a
16-foot steam boat.  I was inspired to build the calliope having seen
one in Maryborough, Queensland, when on holiday some years ago.

I also made initial enquiries through MMD and got excellent advice
and encouragement in the early stages on how to combine 18th and 21st
century technology.  The end result is a calliope where the pipes are
mechanically operated by keys pulled down by 24-volt solenoids actuated
by a 32-note MTP1 MIDI controller from John Wale in the UK,
http://www.j-omega.co.uk/ .  You will probably have to actuate the
solenoids through relays triggered by the MTP1.

The MTP1 needs to be fed tunes in MIDI format from a computer or from a
device known as a MIDI sequencer which reads tunes off floppy disks and
were made by Casio, Roland, Yamaha, etc.  MIDI format is not available
on CDs.

I have a Macintosh computer and run MIDI through a programme, called
Intuem, downloaded from the 'Net.  I understand there are PC
equivalents (not as good of course!).

I can play directly from the keyboard but, because there are only 16
notes, for automatic playing I must firstly arrange and record tunes
in 16-note MIDI format onto the computers hard drive or a floppy disk.
There are hundreds of tunes in MIDI format on the net but they are all
for a full keyboard.  However, because many 'busker' or 'street organs'
have only 20 or 32 notes, there are specialist arrangers who sell tunes
especially for these configurations. See  http://www.alanpell.com/ and
http://www.melright.com/ to give you some idea of what is available.
I am currently increasing my calliope to 20 notes to take advantage
of this.

Finally, I must confess that, having had my calliope operational for
the last two years, I have only run it on steam once.  It makes quite
enough noise on 1 or 2 psi air from a tellus on blow, and it fetches
a crowd at steam meets or model engineers exhibitions without any
trouble.  The neighbours also need to be kept in mind.

I assume your bells are adjustable at the mouth (from about 3 mm to
20 mm) and voicing them for even 25 psi steam is a b#@@*r of a job.
They also are quite demanding on the supply.

I loved the order from the Captain of one of the Mississippi
sternwheelers that "the calliope is not to be played while the vessel
was manoeuvring!"

Have attached a picture of my calliope in an early 14-note format.
Best of luck and hope the above some help.

Cheers
John Beauchamp
New Zealand