Earlier quoted context omitted.
In classical music, the performance is of course unique, but the piece is not. What I mean is, even if the arrangement has changed for a particular piece, the underlying score, the foundation is same. As you know, classical music is layered. It can be scaled for different sized orchestras, which can be akin to tessellation in graphics. You can add more nuanced scores or details if your orchestra has enough members. O…
But that still had nothing to do with comparing lossy vs lossless, or am I misunderstanding you? How does a live performance that you hear with your ears at a specific place in a room help you pick out missing parts in a different recording, played by different people in a different place, recorded with multiple mics and then mixed and mastered?
In a proper concert hall, sound is expected to be homogenous, so you should be able listen to the orchestra equally well, with the same sound balance (or mix) regardless of the place you sit. Similarly, recordings are done from suspended or positioned (and ideally tuned) mics, so you can capture the orchestra as someone sitting in the audience. At least this is how our performances were recorded.
The mastering is then done to match the recorded sound to the hall's sound, and balance any imperfections or clean the orchestra's inner talk between pieces (yes, we communicate a lot :D ).
When you listen an orchestra live, you will have a lossless blueprint of the piece in your mind (track by track if you can separate the instruments). If you can get a recording of the same performance, you can compare it with the live performance. That's absolutely correct.
But if you listen to a recording of a different orchestra playing the same piece, the arrangement and instrumentation will be same (you may have 8 violins instead of 12 but, violins won't be changed by violas most of the time). So, the atmosphere of the piece will be the same. Assuming the recording is done by competent folks, the spectrum would be the same (~20Hz -> ~20Khz roughly).
After some point, even if you're listening to a different orchestra, you can start to point to the things that should be there. It's very hard to describe, but every instrument has a base sound and details on top of it (you can tell they're all trumpets, but different brands or models. Similarly you can tell they're double basses but they're different in some ways). That base sound starts to erode too when you have a lossy compression, and in turn it affects the sound of the piece, regardless of the finer details (which are mostly affected by resins, bows, styles, etc.).
It's a "these two instruments shouldn't interact like this in this piece. Something is missing!" kind of feeling. This missing part is either something at the high or low end, almost an harmonic. It's not noticeable unless you're looking for it, but it's there.
That difference can be clearly heard by re-encoding a FLAC as a high bitrate MP3 and taking their differences. It's a hiss-like sound by contains a lot of the said harmonics and you can almost listen to the piece just by listening to it. Someone did that and published the differences, but it was some years ago. I'm not sure I can replicate or find the article. That article took differences of the exact same recording but, it can be applied by your brain to different recordings after some time.
Hope I've succeeded to clarify it somewhat. It's something very hard to describe by words. Please ask more questions if you want to. :) I'd be happy to try more.