Being in the middle of MIDIfying my Frati-Hymnia Orchestrion, the
recent thread on this subject triggered me to write this letter.

When I started the restoration of the Frati, about six years ago, I
inserted fiber optics in the existing holes of the wooden tracker bar.
On the bottom side of the tracker bar, where the holes are zigzagged in
four rows, I inserted phototransistors.  These receive light from a 50
cm long lamp, mounted in front of the tracker bar, when punched holes
in the paper roll pass by.

The phototransistors actuate inexpensive surplus 24-volt relays by
means of a simple electronic circuit and type ULN relay driver ICs
(7 in one package, including 'free wheel' snubber diodes :)).

These relays, in turn, lift the primary valves of the stack by a short
piece of stiff copper wire, soldered to the moving armature of the
relays.  So these relays have no electrical switching function anymore,
and one could remove the electrical contacts if they are not part of
the spring action of the relays.  From here everything works
pneumatically, as original.

All this was done with no MIDI in mind but merely of time, to get the
orchestrion playing as fast as possible in order to let the 93-year-old
lady, who once owned the Frati, hear the result, and this was realised
last summer.  (Designing electronic circuits was my daily bread for
more than 30 years.)

Pleased with the results so far, later on the idea of MIDIfying came
up.  Searching with Google.com I came across the "Do it Yourself" MIDI
web site of Thorsten Klose, and I mailed him about my Frati and
MIDIfying it.  Thorsten was so kind to help me realize this.  He
designed the Midio128 for this purpose, just for free.  That is, he
wrote the program and burned the PIC for me.  I designed and made the
PCB in my home shop.

See the results at http://www.ucapps.de/midio128.html  Click on
fratipcb.jpg on the bottom of this page to see my homemade PCB.  I know
it doesn't look nice but it works.

The Midio128 is a very flexible MIDI interface.  It can handle a
maximum of 128 inputs and outputs.  These are scanned within 500 usec!
It can record and playback simultaneously the MIDI events assigned to
the pins.  What's more important, you can easily modify the MIDI events
assigned to the pins, later on, to adapt it for your typical
application, by editing a *.ini file and then generating a *.syx file
with perl.exe and transferring this to the flash memory of the PIC via
your MIDI cable with midiox.exe.

All these programs are free available on the net.  Thorsten Klose
explains this on his site in more detail.  You don't need to learn to
write a program; I cannot either.  You're just typing the *.ini file
as I type this mail right now.

The only thing you need is to know the hexadecimal codes that are used
for the MIDI events.  As an example: The sustain pedal of the Frati is
hole 12 of the tracker bar.  So I assigned the Hex code of the sustain
pedal, being B0 40, to pin 12 which happens to be also pin 12 of the
PCB ;)  So when recording a roll, every time the sustain pedal is
activated, you see the well-known Pedal symbol in the scores of Cakewalk
or whatever sequencing program you use and of course also the note's
that are played.

So what are the possibilities of this MIDI interface?

1.  First of all I can play/scan my rolls and record them in MIDI format
to archive them.

2.  I can play the recorded MIDI file and you will hear the roll
playing without being there.

3.  If I could borrow some of the 200+ Frati rolls at a museum in Berlin
they could also be archived.

4.  Other compositions in MIDI file format can be played.

5.  By attaching a MIDI keyboard to the MIDI interface one can play the
orchestrion live, along with an accompanying rhythm and voice changes,
and record this happening for later use.  (There is still a minor
imperfection of the existing circuit for this application.)

Tracker bar holes 16-20 play the notes F#-G-G#-A-A#-B, two octaves
below middle C.  Together with hole #8 these notes are shifted half
an octave lower, so C-C#-D-D#-E-F are than played instead. (Do we today
call this multiplexing?)  With hole #4 these notes are shifted a whole
octave downwards; obviously, this trick was done to reduce the number
of tracker bar holes.  Is this also done with piano players?

By the way, when I count all the notes the piano can play this way,
I come up with the number of 65.  Sounds familiar.

These multiplexed notes were not presented in Cakewalk as such.  To
handle this complexity I designed an additional circuit that does the
same as the Frati does in a pneumatic fashion.  I used bi-directional
analogue switches, like CMOS 4053s and 4066s, that switch the pins
16-20 to another group of pins with MIDI events notes C-C#-D-D# -E-F
when hole 8 is active and so on.

The circuit works also in the other direction.  When playing back a
MIDI file, holes #8 or #4 are also activated when notes are playing
that where recorded, derived from this combination.  Just last week I
finished etching, drilling, soldering and testing this board.

So when you consider MIDIfying your player and you are not afraid of
soldering component's on a PCB or you have somebody that can do it for
you, you might consider the Midio128.  The Midibox forum is also a
possibility to inform you if somebody nearby can help you.

Thorsten Klose is a great guy.  He will burn the PIC for you as you can
find out on his web site.

If you want only to play MIDI files on your player you can leave out the
shift registers that are for recording MIDI data.  Maybe you can
construct a tiny T-node, as mentioned earlier in MMD, on the bottom
side of your tracker bar, that is opened with a modified relay as I
did.

Don't rush into this.  The most important thing is the electronic to
pneumatic interface.  First built a test-setup on a small scale and do
extensive tests under worst-case situations before going further.
Simulating worst case situations can be done by reducing the voltage
applied to the relays and/or increasing the vacuum level of your player
and note where failures occur.

Kind greetings from Holland

Willy van der Reijden

 [ See the photos of Willy's magnet valve at the MMD Tech Site,
 [ [ "Valves & Pneumatic Controls: Magnet Valves..." at
 [ http://mmd.foxtail.com/Tech/  -- Robbie