I have some comments regarding the Duo-Art thread.  I am aware of
four different Duo-Art test rolls, and they all have different
standards of chord tests.  The most common test roll is the 1927
"Audiographic" tester which is intended for the 80-note action stacks.
Before this roll, there was the 1921 Electric Duo-Art Tester which was
meant for the 88-note stacks used at that time.

My friend Jeff Wood has an early Duo-Art test roll from around 1914
and, finally, I have a rather strange roll called a "Votey Test Roll"
that tests both 88- and 65-note rolls and includes some Duo-Art tests.
I just read in MMD that Larry Norman is referring to a 1919 test roll,
which is one that I have not encountered so far.

I have written down notes to myself describing the standards of the
1921 and 1927 test rolls, and they are as follows.  (The Y and N stand
for yes and no, which means the chord plays or does not play.  When
two numbers are separated by a slash (/) it means that the two chords
of that test have different numbers of notes.)

1921 Tester - Accompaniment
  Zero level: 3N
  First: 3Y 4N
  Second: 4Y 7N
  Fourth: 8Y   9/10 N

1921 Tester - Theme
  Zero: 3Y  6/7 N
  First: 4Y   6N
  Second: 5Y  9N
  Fourth: 7Y  13/12 N

1927 Tester - Accompaniment
  Zero: 8N
  First: 3Y  5N
  Second: 4Y  8N
  Fourth: 7Y  14/12 N

1927 Tester - Theme
  Zero: 4y  6/7 N
  First: 4/5 Y    7/8 N
  Second: 5Y   10 N
  Fourth: 7/10 Y   15/13 N

Naturally, to get the best accuracy, you need to use the right test
roll, and as far as I know, the only one that has ever been recut
is the 1927 "Audiographic" roll.  I am willing to lend my original
test rolls to be scanned so that we can all have this information.
It certainly would help to use the same chords as in the roll, as
a chord of any three or so notes may not be the same as the specific
one Aeolian used.

Randolph Herr