It is not all that common where the Haus-Frau and I like the same music.Trinity Sessions by the Cowboy Junkies would be a good example of “blackness as ambience” that most of us have heard.
^That Cowboy Junkies^ is a great example of music we both like, as well as the blackness.
However “blackness” might be worded as “space” and “quietness”… IME.
It seems like it is back to the “Hippocratic” phrase that @tima threw out in the last week.
Once can have speakers with distortion that kills the “blackness” effect.
Or have electronics that kills it.
And then the room can kill it.
(Certainly bad speaker placement can kill it - at least in all the rooms I have been in.)
That “space and quietness” is something that, when it appears, I know that something nice is really starting to happen.
It is not always there, and it’s way easier to lose that it is to get.
Ha ha “speaks volumes” ……
The very fact that the OP needed to ask the question what it actually means, a very legitimate question indeed, speaks volumes.
It may also be that the OP has not heard it?
I am not sure that all electronics and all speakers can achieve it - but “I dunno”.
The systems with a “fullness of sound” and ones that are “bright/sharp”, seem to tend to not achieve it easily.
There may be something with “dynamic sounding” that can also run counter to “blackness of sound”.
If people are listening to those sorts of systems, then it might be that they are trading off things that prevent the “quietness”?