I was just reminded of a Gene Pitney Greatest Hits CD I have, which was purchased for almost nothing at a flea market - one of those 'no name' European efforts that, ummm, are really legit ... . And it's a shocker - from needle drops, and the gorilla who did it decided that it needed noise reduction to "improve it" - the latter was done in such a clumsy and obvious way that normally it renders many of the songs almost unlistenable - the massive level and noise pumping artifacts from the crudeness of this doctoring is something to behold!
So, what's the point here? Well, on midfi playback these severe anomalies are largely obscured because the replay will not have the resolution to show up what's happening; the recording sounds quite reasonable and can be enjoyed for what it was intended for: casual, background listening. But on an ambitious rig that's "highly detailed", these tracks are a nightmare! One grinds the teeth, being constantly aware of the damage wrought upon the original recording - which song it is barely breaks through into the consciousness, it's just "too much work" dealing with the distortion which is constantly drawing attention to itself.
OK, throw it into the bin then!! ... ... but, not so fast! Turns out that 'convincing' playback rescues the recording - gets it back into the zone that the midfi playback of the album delivered; meaning, you can hear that there are issues if you choose to focus on such, but the musical message comes through, loud and clear. How can this be? Well, think of the recording as having two 'spaces': that of the original recording, and that of the terrible, hamfisted mangling done in the "mastering" of this "copy" - it's as if one is listening to two recordings, overlaid upon each other.
If the system is less than convincing in quality then it is far, far easier to register the "mastering recording" in the listening, the "recording of the music" is largely lost, buried in the 'noise' of the other "recording". But when the quality of the playback is sufficient then the other 'acoustic' asserts itself, that of the original recording - you "hear" the song, and not what was done to damage the information of the track.
I have been fascinated by the variation in the subjective impact of these tracks - I asked the other person listening to a quality replay of one if the problems disturbed them, and they said, "What problems?" ...