Hi all,

I have some questions about roll playback speeds... here goes:

When music rolls are encoded, does the manufacturer assume that the
roll will be played onto a takeup spool with a standard circumference?
Is there a standard?  The takeup spool in my scanner's spoolbox is 5.25"
around.

Are the rolls generally encoded such that when played on a standard-sized
takeup spool, the tempo will remain as intended despite the effect of
the increasing layers of paper accelerating the transport speed?

(say that in one breath :-)

In developing my roll scanner, I seem to notice BOTH possibilities occurring-
some rolls seemed to get faster, some seemed fairly steady.

I'm sure there are other factors at play too, like the possibility of
the old paper changing thickness due to atmospheric conditions, brittleness,
and so on.

It occurred to me that I could include a function in my scanning software
to adjust for the speed-up effect mathematically... Perhaps I could
measure the diameter of the takeup spool (with music) at the end of a roll,
then have the software correct the timing in the scanned data based on
that measurement, the duration of the piece, and the original circumference
of the takeup spool.

But I am trying to avoid functions that alter the data too much-- I am
trying to preserve the rolls in their original form as much as possible.

Anyway- I haven't seen much reference to these problems in the various
books on player piano restoration/repair.

If anyone could shed some light on this, I'd appreciate it.


Mark

ps. On a related note, I know that the tempo control is supposed to be
calibrated such that 70 = 7 feet per minute, 80 = 8 feet per minute, etc.
Am I correct in figuring this measurement should be done with a nearly
empty takeup spool?