Its not the mastering… mastering is only a final tweak to whatever file the last company/process received to then make the sellable format. The word “Master” implies something it is not. The tape that is the “best”, is usually the “Source Tape”… goes by a few names. This is the mixdown from production. Folks incorrectly think this is the master… it is not. A master may be a copy of a copy of a copy… that last tape, or whatever, is given to someone/company to tweak it for final conversion/transfer to a sellable medium… that medium could be a downloadable file, or squeezed onto a CD… or SACD etc. That last step is called Mastering… a word that is very misunderstood. Mastering may include compression, expansion, equalization, limiting, stereoizing… whatever.
Note I said “usually” the source tape is the best… but not always. George Martin was furious when someone put out Beatles releases (one of the many re-re-re-re release cycles) and did not master the tape. The intent was to put out the “best” possible sound. Well… Mr Martin purposly mixed down the Beatles “hot” or unnaturally bright. He did this because he knew the tape would be continually copied multi-generation and distributed around the world to record processing plants. When tapes are copied and then copies made of that one, the first thing to go is the top end. Mr Martin expected whoever to then cut the discs to apply equalization to lower (if needed at this point) the high frequencies… (this is mastering). So the moral: not all source tapes are good for distribution.
I have a German print of Rubber Soul where the left channel is completely… yes completely different from the right. The intent was to mix it down for mono or processed for stereo. Cool but terrible.
Check this out for a bit more: My disappointment with Hi-Rez - am I expecting too much? Paul McCartney
Bruce in Philly