I think "air around instruments" is sort of a mixed metaphor, if you will, so we end up talking about two different things here. Having a system reproduce voices clearly separated in space is a soundstaging feature, and one, IMO, that is not terribly realistic, as others have noted. Still, I'd rather have it than not. Soundstaging "tricks" are often very pleasurable surrogates for the natural spaciousness and grandeur (not to mention the visual aspect) of live music that most of us cannot hope to reproduce in our homes. I'm willing to be duped by good soundstaging.
Air, it seems to me, is not a soundstaging feature. It has to do with fine detail that captures the interior texture of sounds. I think I'm with Sharri here. A system that does "air" well conveys the sense that music is aural painting of air, that the sounds are illumined and alive on the inside. It's easier to think of what lack of "air" is: a lot of reproduced music gives dynamics, shape and surface texture to the sound, but ultimately the sounds are rather dense and inert on the inside. My four-bit words on the subject.
Air, it seems to me, is not a soundstaging feature. It has to do with fine detail that captures the interior texture of sounds. I think I'm with Sharri here. A system that does "air" well conveys the sense that music is aural painting of air, that the sounds are illumined and alive on the inside. It's easier to think of what lack of "air" is: a lot of reproduced music gives dynamics, shape and surface texture to the sound, but ultimately the sounds are rather dense and inert on the inside. My four-bit words on the subject.