Do we really know what "Live" music sounds like?

Yes.

I don’t care much for the suggestion of a salesperson playing something in the store. That could be a very forgettable experience. [edit - and now I read @feldmen4  thought.  Quite so.]

Another rather el-cheapo option - seek out a church (however defined) where they have a resident choir accompanied by a pipe organ.

If sitting through the service isn’t your calling, they rehearse, you know, and sometimes may have special performances of some choral piece/s by JS Bach if your lucky.

For years, I was totally into guitar rock, including concerts. Some were pretty good, but for the most part the bands sounded better on record or CD rather than live. The vocals were often drowned out by the instruments, decreasing the fun of hearing the music live. I was particularly disappointed when I saw the band, Three Doors Down, in concert, as the vocals were non-comprehensible (even if you knew the words) and all together it was about as pleasant as having a chain saw operated beside my ear. I was very disappointed, though I continue to enjoy the band’s recordings.

Acoustic music and low-amplified bands are usually much better, though that depends upon the artist. In recent years, I attended concerts by Bob Dylan and “Willie Nelson and Family” and both were snorefests! Utterly disappointing. When I see someone claiming “Attend live music, then seek to have your audio system sound like that”, I know they cannot be referring to concerts like these. Best that your system not sound like that.

I’ve never been into classical or symphonic music, but I bet that is what the advocates for live music are referring to, The closest I have come in recent years were concerts by Tony Bennett and LeAnn Rimes, both backed by 3-4 piece bands. When the quality of the artist is that good, you don’t need to be blasted out of your seat or strain to hear what is being played or mumbled. I regret that I never attended a Linda Ronstadt concert, as I’m certain the power and clarity of her voice would shine through even during rambunctious guitar riffs.

P.S.  After writing the above, I read the referenced article (I’m lazy that way).  It was interesting read and made good points.  It was definitely worth reading and I thank the OP for bringing it to our attention, 

If I’m not mistaken, amplifiers are part of every non-acoustic instrument. With a great deal of effort, I’ve learned to appreciate opera; but the amplified human voice is to me, far more listenable in any venue larger than a coffee house.

That said, I think it’s impossible to know what live music sounds like until/unless you actually hear it, simply because no listening room's acoustics approximates those of the broad range of acoustic environments in which one hears live music. Nevertheless, psycho-acoustic phenomena more than adequately compensates for that deficit . . . provided the playback system is linear in all respects and capable of reproducing the frequency extremes included in all live music.

My preference is two-channel analogue for the ultrasonic frequencies that convey the emotion and sound staging the performers and recording engineers intended their listeners to experience. I prefer valve amplification on accounta' it augments my GFA heating system at my sedentary listening position enough to keep me comfortable during cold winter months.

Besides, tube rolling is kinda’ fun.😀

At least with live music one will not encounter 'sibilance' with vocals. But back in the days of 70's live Rock gigs the sound was so awful that I remember suffering from sound buzzing in my ears for a long time after the concert.  Especially the time when I was directly positioned on the side where Ritchie Blackmore's guitar came out of the huge concert speaker, it was good to know the tunes of the songs played in advance because one would not recognise the song actually played live in concert because of the distortion of the loud sound.....!

Coming back to the op’s statement I often find that so called ’live music’ via HiFi System would sound better than the ’studio’ version, because it has the advantage of sounding organic with verve. Sometimes listening to sealed speakers in comparison to ported speakers has the same effect which makes the music more ’immediate’ one of the treasure of the ATC speakers and highlights more how the musicians are playing their instruments. Groups such as Pink Floyd and Dire Straits have done studio and live albums of their same tracks, often the way the tracks have been performed are nearly  identical in Studio mode or Live mode but the sound effect of the ’Live’ mode for me is the instant obvious advantage of that live instant and immediate sound.....