Converting MIDI to Duo-Art
By Richard Vance
Mr. Waring's idea about converting digital piano recordings into reproducing rolls is intriguing, but it may not be easy to do. The dynamic coding on a roll is not a straightforward replica of a theoreti- cal curve representing the relative loudness of each note, as might be the case in a modern electronic system. Roll editors had to use all sorts of tricks, based on long experience and musical judgment, to compensate for the actual behavior of the piano, in order to make the end product come out right.
This process has been extensively commented on in the AMICA Bulletin by modern roll editors. Only one example is the problem (inelegantly called "droop" in pneumatic control theory) where the theoretical "setpoint" of a pressure regulator differs from the actual output pressure as a function of the load -- the number and loudness of notes being controlled. This is must be an especially vexing problem for the Duo-Art editor.
I don't know if any progress has been made to do these compensations by computer rather than by human judgment, but such a program would have to be complex, because there are many complex phenomena in a reproducing piano which have to be allowed for.
Another example of this problem is the placement in time of the punched coding, to compensate for the time delays inherent in a mechanical system. The preset for the binary regulators [the Accompaniment channels] in a Duo-Art is proactive and may not be time-critical in the short term, but the proper position and duration of the snakebite (the accent command) surely must be.
I personally think that one of the editing tricks in the original rolls was to place a single lagging snakebite against a note or chord, producing a subtle partial accent of the note. On old pneumatically scanned recuts, single snakebites ended up 2 or 3 punches long, obliterating that subtlety, and contributing to the "muddiness" of musical effect observed in some recuts when compared with the original.
Richard Vance
[ We have several folks here concerned with this topic, and I think
[ there still exists an un-moderated listserver which Jody created for
[ discussion. Perhaps we can revive it.
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(Message sent Mon 10 Feb 1997, 02:36:20 GMT, from time zone GMT.) |
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