In Digest 960321 David Wasson described his music roll perforator 
and why he wants to modify it for synchronous control.  Among his 
reasons are the need for precise control of the musical Tempo, 
irrespective of the paper speed and distance (his 10-tune rolls are 
quite large and play for at least 30 minutes), and also to permit 
"chain" patterns.  He has already confirmed that re-sampling his 
original song file for a new paper speed (recording the MIDI data 
from one computer to another) causes data corruption.

Here's a fast answer for you, David, and then I'll discuss "why"!

You must substitute a perforator crankshaft signal for the built-in 
timebase clock of your computer/sequencer, so that the data to 
your perforator are synchronized with the paper motion.  There are 
at least two methods for external control or synchronization:

(1) Use a switch on the crankshaft to generate the "MIDI Sync" 
signal which enters the computer via the Printer port or a secondary 
MIDI port.  I think this will cause the sequencer to advance one 
"tick" for each crankshaft revolution.  Check your sequencer 
documentation.

(2) Use a tach disk on the crankshaft to phase-lock an oscillator at 
roughly 1 MHz, and feed this signal into the external clock pin of 
the modem port (substituting for the 1 MHz crystal oscillator of the 
MIDI adapter hardware.)

These methods, or equivalent, will assure that your perforator and 
the computer data file are locked together, synchronously, just as 
the perforator crankshaft moves the sprocket drive of a Master Roll. 
You will need an intermediate computer or "off-line" processing of 
your original MIDI files to apply the Tempo Map data to make a 
Master Roll file, and also to generate the chaining. 

Now I'll talk about the theory...

 - - - Perforated Music Rolls, Part 1 - - - - - - - - -

The process of synchronously duplicating copies of music rolls was
developed in order to assure that each and every production roll is 
identical, and contains the all the data of the Master Roll, 
without corruption.

The Master Roll is, by definition, the template which controls the 
perforator machine.  It is nothing more than a binary data file 
composed of 100-bit "words" which are processed sequentially, one 
word at a time.  Numerical-control (NC) machine tools of the 1960s 
were equipped with similar punched paper tape controls; the "Master 
Roll" consisted of 8-bit words, processed sequentially.  In both 
systems the master roll or tape is advanced by a sprocket wheel, 
with peripheral pins which engage the sprocket holes.  Each cycle of 
the machine advances the master roll one step, or one "word".

It may have been Richard Tonnesen who observed something like, 
"People tend to think of time and distance as being interchangeable."  
The movement of the music roll is somehow equated with the movement 
of the magnetic tape in a cassette.  However, when one examines the 
matter, it is apparent that the speed of the music roll isn't 
constant, and there are only periodic samples of music data -- the 
music has been quantized. 

[ Part 2 will follow soon... -- Robbie Rhodes