Tim Baxter wrote:

> Robbie:  Thanks for your helpful response.  I should not have phrased
> my query in terms of "time" per se.  My brief query to you is: was your
> response written as a general rule for all rolls due to some idiosyn-
> cracy of the Tonnesen's punching (even if copied directly, hole-for-
> hole, from a properly punched roll), or was your response intended for
> me as a MIDI editor?
>
> Thanks,
>
> Tim Baxter

Hi, Tim !   Richard Tonnesen's perforator is normally set-up to advance
the paper 0.0222-inch for each revolution of the crankshaft.  This
results in 45 rows-per-inch.  The hole size is about 0.068-inch diameter,
and a "playback" tracker bar at the customers piano is assumed to have a
hole about 0.045-inch high.

Now imagine a single hole in the paper passing over the hole in the
tracker bar.  The pneumatic valve will be 'on' while the paper moves
the distance of the sum of the height of the tracker-bar hole plus about
one-half of the diameter of the hole in the paper, or 0.045  + 0.068 / 2
= 0.079 .  This distance (0.079) is roughly 3.5 times the advance
distance, or 3.5 x .0222 .

The "general rule" applies to all perforators, but the "specific rule"
above is just for Tonnesen's specific perforator.  The parameters in the
formula would change if you were to use, say, 20 rows-per-inch, which is
the rather coarse format used by many New York and New Jersey firms in
the 1920s, and possibly still in use at QRS.

It's easier to perform the truncation operation in the MIDI file, but it
takes a little math to predict the effect.  Fortunately, you can use
"View" to check the results: it displays each punch step just as though
it was a 1920s "3-to-1" master roll.

Thanks for writing, and best wishes in your project.  We're all happy to
help you if we can.

Robbie Rhodes

 [ Tim's reply: ]

> Robbie -- This is the most lucid explanation yet for my non-physics
> brain (damn that liberal arts education!!).  I finally get it!
>
> My contribution to the greater glory of MMD will follow, after all
> the help I've been given!

 [ Keep us posted on your progress, Tim, and good luck!  -- Robbie