Hello all,  This letter is in response to John Kleinbauer's note in
Digest 980523 and to Jody's request for a description of my attempt to
make music on the piano and organ via computer and rolls.

Being a frustrated (no talent, after practicing for over 50 years)
piano player, but loving ragtime and 1890-1920's dance tunes, I decided
to see if I could make these instruments play from the computer, and
from nickelodeon rolls.

Starting with a Simplex player piano which I bought for $50 when I was
an 18-year-old kid in 1948, a Yamaha MC-600 electronic organ, and an
old Radio Shack model III TRS-80 computer (which has a connector
directly accessing its buffered parallel buss), I designed a simple
interface circuit using, as John did, a 74154 IC decoder.

In this case though, the 74154 was used only as a 4-bit address decoder
which controlled the "chip select" inputs on three sets of eight 74374
octal "D" latches, which were wired to the computers 8-bit data buss.
This enabled selection of any combination of 1 to 64 notes.  (The
Simplex is a 65 note player).

Software to control the thing was written in BASIC and required less
than 20 lines of code for the "boiler plate" section.  It takes an
average of 2-3 hours to code in a typical tune.  About 700 tunes have
been programmed so far, all oldies.

A set of solenoid valves was made to replace the tracker bar on the
piano.  These were made from small surplus solenoids with rubber pads
cemented on their plungers, which rest on the top open ends of brass
tubes, which in turn are connected to the player stack in the piano.
The solenoids are driven by a series of 75492 IC LED drivers,
controlled by the decoder circuitry.

Since the organ keyboard is wired similar to that of a computer
keyboard matrix, a converter circuit was built to "decode" the 64 lines
that control the piano.

I have a collection of 60 type "A" nickelodeon rolls (10 tunes per
roll); these are "read" by a photoelectric tracker bar, whose infra-red
sensitive (more surplus - not affected by room lighting) photo-cells
are fed into the computer interface board, but are triggered by a 3-kHz
clock generator so the instruments respond almost instantly to the hole
patterns in the roll.

Now, if I had a lot of money, it could all have been done with MIDI,
but this was fun too.  Will be glad to share more details with
interested parties.  Visitors are welcome, bring your own earplugs...
I'm in Temple City, Calif., near Pasadena.

Lee Roan
LROAN2@aol.com