Hi Ed
ethereal sounds is one of Eventide's specialties. You can get many of them, using plex verbs/shifters/ring mods/multi tap delays.
These fx are so editable you can even edit the reverb internal delay lines in Expert mode: yes reverb is made w/delay lines (true for any digital reverb)…Eventide is the only processor that allows you to even tweak these delays, to simulate reflections in the way you like.
all the best
I
