Air is the space around individual instruments. When you hear halos I would guess that you are exciting the angels :)
Detlof your explanation is interesting however I always referred to this effect as the natural decay. Sometimes when I listen to this effect and I certainly hear it in spades on some recordings, it appears the decay may be a bit longer than I note with live music as though there is some type of reverberant effect added to the recording. Even a reverberant hall doesn't seem to hang on to notes as long as certain recordings do. At least I can't recall hearing it to the same degree. Live seems a bit faster.
Detlof your explanation is interesting however I always referred to this effect as the natural decay. Sometimes when I listen to this effect and I certainly hear it in spades on some recordings, it appears the decay may be a bit longer than I note with live music as though there is some type of reverberant effect added to the recording. Even a reverberant hall doesn't seem to hang on to notes as long as certain recordings do. At least I can't recall hearing it to the same degree. Live seems a bit faster.