Regarding the Hi-Fi (HIGH FIDELITY) fever point-of-view, I believe we talk about the first generation of MASTERTAPE,
that's means the really original first recording of MASTER-TAPE instead of those duplicate SLAVE COPY,
as we all know the more MASTERTAPE playing-back the more wear-and-tear meaning sound quality dropping,
if we really run out of original first MASTERTAPE, of course SLAVE COPY is still better than nothing
same as film, sometimes those oldies movie, we can still find some good quality of SLAVE COPY privately with additional unused tracks to restore:
such as the famous black and white German movie THE METROPOLIS with 25 minutes extra unseen footage