Take-up Spool Tempo Compensation
By David Wasson
I have been following with great interest the discussion of perforator step size. During this discussion, nobody so far has mentioned the topic of tempo compensation. I'm sure everyone realizes that as a music roll plays, the take-up spool increases in diameter, causing the paper to travel faster towards the end of a roll.
I am now aware, by virtue of this forum, that Ampico paid great attention to music roll accuracy. I was sure that Ampico was well aware of compensating for the change in paper speed over the duration of a tune. So I did some investigation to see what they had done. To my surprise, all of the rolls I checked had the same distance between beats from the beginning of the roll to the end. These rolls were not tempo-compensated. Or is there something else going on? This sort of non-tempo-compensation reminds me of my first hand-cut rolls. Tempo compensation throughout the duration of a tune is difficult and inconvenient to do by hand.
-- Why didn't Ampico, with precision automatic perforators, compensate the tempo?
-- Do all Ampico pianos have a take-up spool with the same diameter?
The subject of perforator step caused me to do this investigation. Rolls produced by Wurlitzer are definitely tempo compensated throughout the entire length of the music roll. If you try to put a number on the step size you will discover that the step size changes continuously, and there is no number that you can assign to the step size. The distance between beats on a roll produced by a Wurlitzer perforator will grow towards the end of a tune. I believe that the Wurlitzer perforator mechanism which created the variable step size was described by Matthew Caulfield.
If someone has comments on why Wurlitzer tempo compensated music rolls and Ampico seemingly did not, I would be very interested to know.
Sincerely, David F. Wasson
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(Message sent Fri 6 Dec 1996, 23:26:30 GMT, from time zone GMT-0800.) |
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