What exactly is "real"? These same variations also happen with unamplified acoustic music. I own several flutes that all sound different, and each instrument sounds different when playing in different rooms, or sitting at a different location in the group. Our cello player once tried a different kind of strings that made him sound more like a recording: a bit more projection (louder), but with a bit of extra HF "zing" added to the timbre.
Have you listened to "Drums and Bells" by Chris Dutz? It's a phenomenal recording having incredibly natural lifelike voicing. It's the most natural realistic drum & percussion I have ever heard in an audio system. I'm curious whether others agree it is lifelike, or perhaps my opinion is just an artifact of my own subjective perception and quirks of my audio system.
For sure, there's a "circle of confusion" even extending in to real sounds for those reasons.
But it seems to me that doesn't disbar all possible assessment of what sounds "natural" or "more real."
If we had a naturally recorded voice and played it through, say, the Revel Salon 2s vs through the speakers on an iphone, surely pretty much everyone will recognize and agree the voice through the Revels sound "more like a real-life voice" even if not perfect. Our auditory memory is unreliable...but not wholly unreliable. It gets more unreliable as you scale down the differing sonic characteristics to ever more similar...but becomes more reliable as you scale those differences upward. In a blind test, I'm not going to mistake Godzilla's famous roar with Kermit The Frog. I can recognize my mother's voice on the phone, or any number of sonic environments. So while it is true and something of a justifiable shibboleth in objective circles "our auditory memory is unreliable" it seems to me we still need to maintain a sense of proportion when making that claim. (And where it stops getting from "pretty reliable" to "simply can't trust it at all" I'm no position to say).
But, again, it doesn't seem like our auditory memory is so bad as to disbar any number of cases where we'd agree "X sounds more real than Y."
As to "what exactly is real?" I'm no arbiter of reality so I can only go by how my own experience of constantly comparing live to reproduced has produced certain perceptions or beliefs. When I hear various instruments being played and I close my eyes, the characteristics that stand our is how timbrally varied and specific it sounds - that instrument made of wood just *sounds* like wood, the drum cymbals sound of real metal, the acoustic guitar strings sound metallic, wholly different from the material the drummer is striking on his. snare, etc. That is the impression that live sound sources leave with me every single time I close my eyes and examine it.
When I close my eyes and examine the sound coming from a speaker, it's not that I know exactly what any particular instrument sounded exactly like in front of the microphones. But I DO know, I believe, that they are playing instruments I'm generally familiar with hearing live and that the live instruments would have a distinctiveness that I'm not hearing through the speaker. So it's not so much "I know exactly what those particular instruments in the musician's hands sounded like in real life" but more "I have a good idea by now how instruments
tend to sound in real life."
And some speakers tend to be so off that I never, ever once get the "I could believe it" sensation where some can produce this sensation.
(It also helps to have recorded and played back instruments one is very familiar with on various speakers. That takes a little bit of the variables out where you actually know what that instrument sounds like. Some speakers to my ears produce my acoustic guitar like *something clear being strummed in front of me* where some few produce a timbre that strikes me more like *that's how it SOUNDS in real life* - like the color being adjusted from "off" to "accurate" on a TV or a photograph).
I just came back from a pal's house where I brought over some records I was listening to on my MBL speakers, e.g. a Bruce Cockburn album with a track of a single acoustic guitar piece. In either the "open eyes" or "closed eyes" not for a second did I get the "that could be a real guitar" sensation from what I heard. Whereas the life-like impression and timbral convincingness seemed to come almost effortlessly listening through the MBLs.
It would be great to have a lab where I had both sets of speakers, a recording of an acoustic guitar playing and compare both speakers, blinded, to the sound of the real guitar playing to see if my subjective impressions hold up. But....lacking such facilities, and not having access to any other science (that I'm aware of) concerning blind testing of live vs recorded....for someone who IS interested in experiencing realism, my "can I believe this, is it giving me characteristics of live instruments that sound 'right' to my ears" is the best I've got.