It's called PANNING. Most stereo people know the word, so why do they not use it, and instead opt for the ridiculous SOUNDSTAGE nonsense?So what term (if not soundstage) do you use for where you place instruments horizontally in a mix?
There is only L-R panning, and whatever depth you can fool people into believing exists through reverb.
But reverb is (or was more in the past) used so liberally all of the content sounded buried in reverb.
The rest are lies told to you by the home stereo community.