What does the audio term 'air' mean?

I have had an audio system of one kind or another for more than sixty years. My first one in high school was a Sears Silvertone two speaker stereo that folded into a suitcase. I took it to college with me. Air was not even something I thought about, yet I think I enjoyed music perhaps a bit more than I do now. That had to do with juice in my brain and the newness of life and music. 

I have taken the same steps as most audiophiles, spending first in the hundreds of dollars, then in the thousands of dollars, and now in the tens of thousands of dollars. I doubt that I will ever own an audio system over a hundred thousand dollars, but I very well may have put that much into my system with constant upgrades. 

I think I began to notice what I call 'air' when I could tell the difference between vinyl and digital. I am talking about the digital of yesteryear, and perhaps a bit now, too. Many years ago, album producers began putting out vinyl that was marked digital. When I questioned the salesperson, he said it was just better. Listen to it myself. At the time, it did sound more accurate. More defined. The quality of 'air' was not on my mind.

It was when I began to upgrade my analogue front end that I thought that vinyl sounded better than digital. Of course, digital was still pretty crude back then. My system was still in the thousands of dollar category. NAD receiver, Energy speakers, and I purchased a used Rega 3 for several hundred dollars. I could not really say why I thought analogue sounded better. I told my friends it was more 'present.'

When I reached the point where I could hear a soundstage, the question of space came to mind. How high, how wide, how deep? Later, I began to hear instrument placement. But that still didn't beg the question of 'air,' even though there was something separating the instruments. I think I was still thinking in terms of space.

When I went stereo shopping with friends who had more money than I did, I was able to listen to more expensive speakers. Dynaudio were becoming one of the most popular speakers. I immediately didn't like them. I couldn't say why. They were tight, had good bass, and threw a nice soundstage. I think they sounded 'hard' to me. The attacks were very tight, but not very forgiving. It was not the way I heard music.

I went shopping with a friend who had gotten an inheritance and we listened to Wilson Sophias. He was hooked and bought them. To my ear they sounded a bit dry. So did B&Ws, and I came to understand that their was a British sound which people thought was accurate. And it did sound accurate to my ear, but not quite like music.

Music not only travels on air, it is vibrations on air. And the more I listen to live unamplified music, the more I hear that it is not as well defined as certain 'accurate' speakers portray it. A lot happens as it travels through the air. In orchestral music the instruments get jumbled together to some degree. In other words, there really is not space between instruments, however, they do seem defined within the soup of air that hits my ear.

Now that I own a pretty decent system, Sonus Faber Olympica Nova 5 speakers, VPI Prime Signature 21 turntable, Audio Research Ph-7 phono preamp, Pass XP-30 preamp, and a most wonderful amp that most of you have probably never heard of, a Hovland Radia, I sometimes marvel at the air I hear both in analogue and digital. I have a Moon 280 D streamer and on really well recorded, high bit-rate sampling recordings, I can hear the air that I hear on analogue recordings.

But I really don't know how to explain this wonderful thing I hear. I call it 'air' because I have heard that word used by audio writers. But what is it exactly? I wonder if any of you can define it better than I have.