In MMD 021102, Harald Mueller enquired about the speed of a Triola
music roll.  I have taken some measurements this evening on Roll 1397,
"Harre meine Seele", a rather slow German chorale.  The roll is 6.3 m
(20.5 ft) long, and I think it sounds comfortable when cranked through
in 2 minutes and 30 seconds.  The roll speed is thus 42 mm/sec, or 8.2
feet per minute.  Other rolls may vary.

It is important to note that the Triola rolls gradually lengthen the
note slots to compensate for the effects of paper build-up on the
take-up spool.  The heavy paper (0.0045" thick) builds up from an
initial diameter of 1.00" to 1.65" with 20 feet on the spool, giving an
increase of 60% in linear speed.  The note slots are lengthened in the
same proportion to keep the tempo constant.  A note that measures 33 mm
at the start of the roll is 53 mm when the phrase is repeated near the
end.  The step advance seems to be about 1 mm at the start of the roll,
and appears to increase uniformly throughout the length.

I would be interested to know more about Harald's arrangements, and how
they are to be punched.

John Wolff.
Melbourne, Australia.