Hole-for-hole Replication
By Robbie Rhodes
Craig Brougher indicates that some of his recut Ampico rolls sometimes don't sound quite as clean and crisp as do the original rolls.
The recut Ampico roll sounds muddy or lifeless because the holes which command the accents are displaced the wrong distance from the note holes. This is *critical*. The replicating process must preserve the timing to less than about 20 milliseconds, which is about 0.030 inch at Tempo 80. The step distance of an Ampico roll is also about 0.030 inch, therefore no errors can be tolerated!
Richard Tonneson samples the input roll every 0.022 inch; his asynchro- nous process is accurate to plus or minus one sample maximum error, therefore his normal copies are accurate to within 0.044 inch. Most of the time the accents are okay, but every so often an accent command is late, and the music is lifeless. Richard is well aware of the problem and has participated in several experiments with Wayne Stahnke and me to develop better accuracy, but his market won't yet support the added costs for high-precision copying.
So there's the answer, Craig. Hole-for-hole copies _can_ be produced, but they're too expensive currently. The producer of a recutting project knows that most of his customers won't complain about occasional missing accents, but they surely _will_ object if the price seems too high!
Practically all of the piano rolls produced in America were made with synchronous copying techniques, in order to assure that each and every product was identical hole-for-hole, and so that the data (the holes) in each production roll matched the data of the edited master roll.
The same philosophy, with similar techniques, was followed in replicating punched cards for the Jacquard loom, the Hollerith "IBM cards", and the punched paper tape for Teletype messages. The replica was acceptable only if the data matched bit-for-bit, hole-for-hole.
Faulty data -- duplicating errors -- in weaving are pretty obvious to the eye, and wouldn't be tolerated by an inspector, and certainly a banker wouldn't tolerate errors in a stack of punched cards containing bank transactions. So why do we consumers tolerate errors in recut piano rolls which don't match hole-for-hole?
It's because most of the time it doesn't offend the ear! Organ music doesn't demand the precision timing that a reproducing piano does, therefore organ music rolls (or books, or barrels) can be replicated asynchronously. So they were, and so they still are.
Robbie Rhodes
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(Message sent Sun 9 Feb 1997, 00:44:42 GMT, from time zone GMT-0800.) |
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