dMaybe this will add some clarity....
OP asks:
is a recording’s soundstage and imaging of individual participants, whether musicians or vocalists, things that one can truly perceive
YES!
depending....
can we actually, from a recording only, determine different musical instruments?
of course.
if not, we desperately need to upgrade our systems, or we ought to take up building ships in botles or fishing.
can we differentiate between vocalists, instruments, and their relative locations on stage or in the venue?
with decent hearing, and a reasonably well setup system, of course.
can we localize where these instruments are on stage from any recording?
depending on the integrity and ability of the recording engineer and the equipment he or she used., with respect to the aforementioned and while in possession of some sembalence of sanity and good hearing, very likely.
OP also asks:
...or are they merely illusions that we all are imagining as some sort of delusion?
I was, and have been, delusional but I got better.
were I delusional listening to 'Harlem Nocturne' could be 'precieved' as perhaps, a Wooly Mamoth seeking a mate in the shadows of a moon lit night.
or a storm of mellon sized flagelant butterflies coming thru the walls of my house while singing Frankie Goes To Hollywood tunes.
.... were I truly delusional all bets are off.
there is art in commercial recordings and why some recording engineers are sought after and some are not.
there are techniques in mastering recordings and in the setup or approach as to the locations of microphones not dedicated to individual instruments or vocalists which help capture presence and artifacts of the venue.
the tricks are in the mix.
maybe another insightful theme could address should live venue recordings identically or very closely emulate the original concert in order to be considered a quality recording?
in some cases it seems this latter notion contains things impossible to properly mix down into the final product.
some aspects or things simply should not or can not logistically be promoted to specific locations.
take the Moody Blues for example. They add from time to time, an orchestra presentation aiding their own artistic content, and they are not the only ones that do this.
The Beatles. Rolling Stones.spirit. Pink Floyd. Quicksilver messenger Service. Spyra Gyra. ' Zepplin. Willie Nelson. Sinatra. Striesand. etc.
should the orchestra be placed in front of the group, behind them, or under them?
if Firesign Theater made every recordign mono would their albums involve the listener nearly as much?
Effects! tricks. techniques. they all add up to the experience we enjoy as a habit, er, uh, pastime.
reproducing and as such, acquiring the 'illusion' with as much inherent organic . tangibility as is possible is the goal for an audio system to routinely exhibit.
we are seeking goose bumps. Jaws on floors. utter disbelief in hearing what we know for a fact is not real, but the presentation has propelled us beyond the threshold of disbelief.
Being deluded can NEVER be a component in qualifying or quantifying these hair raising experiences.
well, not accurately.
as for the idea live concerts are all mono exploits I strongly disagree and ask, Have you ever been to a Pink Floyd show? ever heard a live symphony? heard a Barber Shop Quartet?
in fact, from the rear of the hall it might sound like a monaural demonstration but right down front it is not.
I think the underlying and more important theme here is 'was the recording enjoyable or not?"
indeed, some 'live' concert recordings are not front to back at just one venue, recordings. Little Feat 'Waiting for Columbus' was a compilation taken from various shows during one of their tours. . I so dig that album.