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The Mapleson Cylinders - Program Notes
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Future Restorations
I am often asked about digital restoration of the
Maplesons--whether
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or not that might be the ultimate answer to
rescuing some of the faintest signals. Digital filtering in itself is a very
complex technology, and as yet not well defined. The digital filtering in use
today has employed various techniques, including band splitting, dynamic noise
reduction, deconvolution (as in the Soundstream reprocessings of Caruso
records), and others. It is in any case a very expensive process, requiring
sophisticated software and analysis. In many cases the result is not at all what you would expect. I
attended a demonstration in Washington, D.C., of a digital restoration of the
famous cylinder of the Emperor Franz Josef. Although all the noise of the
recording was gone, so was the sound of the human voice as we are used to
hearing it. The human voice is a complicated instrument, with harmonics,
overtones, timbre, vibrato, and many other characteristics. If any or all of
these elements are deformed, whether digitally or otherwise, the sound is
seriously impaired. (See B. A. Blesser, "Digitization of Audio: A Comparative
Evaluation of Theory, Implementation, and Current Practice," AES Journal, XXVI/10 [1978], 739-771.) The "ambience" or hall sound
of the old Metropolitan Opera House stage is present in the Mapleson
recordings, and is preserved in these transfers, whereas in previous issues it
was not to be heard. In the present state of the technology, digital filtering
for this type of material does not offer any miraculous cures. However, I am
seriously investigating such technologies as digital delta modulation recording
and filtering, voice identification Spectrographic analysis, and other
methodologies that might serve as a yardstick in judging the results.
