Hi All, I've followed this thread fairly closely and I've had the
same nagging question from the beginning. Considering how fast the
events in a reproducing music roll occur and the amount of time it
takes any valve to cycle, won't the addition of a valve, in line with
the expression system, disrupt the expression of the music?
Admittedly, it might only be noticeable to someone with an extremely
refined ear who also has an intimate knowledge of how the music should
sound, but speaking purely in terms of mathematics, the device will
change the timing of the events.
Further, it's my understanding that a fair amount of post-production
editing had to be done to all reproducing rolls in order to 'capture'
the nuances of the pianist's performance. In examples I've seen (see:
2-seconds.jpg), the vacuum level often changes six times in one second.
So, won't anything that delays the timing of those events, even if
it's only by 10ms-20ms, have an effect on the volume of the notes?
Note: In the Ampico Test Roll, a 0.0755" OD hole occurs every 125 msec
at Tempo 80 (8 ft./minute equals 625 msec/inch of travel). In the
Repetition Test, there are 5 perforations per inch, followed by a 1/4"
perforation. Therefore, the repetition rate of the 5 perforations is
8 Hz (or 8 cycles/sec), with perforations occurring every 200 msec.
Based of the diameter of the perforation, the duration of each pulse
(which allows atmosphere into the pouch well to inflate the pouch and
turn the valve 'on') is 75 msec, from start to finish.
John A Tuttle
Brick, New Jersey, USA
[ One second of expression coding on an Ampico roll