The music roll makers of the past determined the Tempo (in my opinion)
not by the tune itself but mainly on how fast they set the paper speed
across the tracker bar.  If the bars in the music are, say, 1.5 inches
long then, for example, that tune will sound "good" at Tempo 40 (4 feet
per minute).  If that same tune was made with the measure bars at 3
inches in length then the Tempo would have to be faster and around
Tempo 90 (example only).

The reproducing piano rolls again set the paper speed for the artist's
recording, they then determined then to stamp the Tempo figure on the
roll.  Persons playing this roll might want the piece a little faster
of slower, but not too much difference.

My experience is in making orchestrion style "O" rolls where the
Tempo is fixed at between 70 to 75.  I have to compensate as more
tunes on the roll are made by increasing the length of the bars with
an acceleration chart I made for that purpose.

For example, on tune No. 4, the "Czardas from Die Fledermaus" of
my new "O" roll SB-6 (not yet in production due to the company's
workload), during the first 42 bars the bar length is 6" at 4/4 time.
The remainder of the 40 bars are in 2/4 time and are only 1.75 inches
long because it is a far faster melody.  The paper speed within this
tune has changed within this tune by maybe 9" per minute due to paper
build up.

There are degrees in which people listen to music of various types;
some will have more knowledge than others, basing this knowledge on
music heard on recordings and live music, so when they are confronted
with music played by a piano roll they will have more idea at what
speed to set the Tempo.

Steve Bentley
Vancouver, British Columbia, Canada