noun from fidelis ‘faithful’
• the degree of exactness with which something is copied or reproduced
New Oxford American Dictionary
Aside from the excellent points brought up by Ron Streicher which are presented on the UPMIXING page of this website, the fidelity of an upmix from mono to stereo is of paramount importance.
When talking about the fidelity, one first thinks of the audio fidelity, i.e. how faithfully the sound quality represents the original musical performance. Of course, one does not wish to introduce audible artifacts, noise, and distortions that would detract from the listening experience.
Of even greater importance is the fidelity of the upmix from mono to stereo as it relates to its faithfulness to the actual original musical performance itself as presented on the historical mono master recording.
The original master recording, and copies thereof, represent a direct link back to the original musical performance. Every note sung, every note played, every sound present in the upmix to stereo must represent the exact same notes sung, played, and present in the original mono recording. If one were to synchronize and compare the stereo upmix to its mono counterpart side-by-side, every note should line up exactly in time. There should be no additional vocals or instrumentation in the resultant upmix. If it wasn’t present in the original recording, any upmix that includes additional vocals or instrumentals would not be faithful to the original master recording!
The widespread availability of digital audio workstation (DAW) software has made it possible for countless individuals to try their hand at audio editing. It is now possible to create stereo mixes that appear, on the surface, to be somewhat faithful to the original mono master recordings. Unfortunately, direct comparisons between the original historical mono master recordings and these new “stereo” mixes reveals that they are not faithful to the original musical content of the historical mono master recordings. While some may find these type of mixes entertaining, these mixes do not respect the musical integrity of the original mono recordings. These type of mixes will usually show up on Public Domain compact disc compilations released from questionable sources. No engineering credits will be supplied. Suggestions of proprietary processes will be made to excuse the lack of technical details regarding the “processing”.
Consumers should always consider the source before concluding that the new stereo mixes that they are hearing are indeed faithful to the original mono recordings.
Fortunately, mono to stereo upmixes made through the use of spectral editing and/or sound source separation are faithful to the original historical mono master recordings. Every note sung, every note played, every sound present appears exactly in time where it should. No additional voices or instruments are added or subtracted. Upmixes from mono to stereo made this way can be directly compared to the original historical mono recordings because they are derived directly from them.
December 27, 2015