Shimmer reverb
A reverb whose tail is fed through a pitch shifter and back in, so each pass climbs an octave higher.
The recipe is a feedback loop: the reverb output runs through a pitch shifter, usually set an octave up, and is fed back into the reverb input. Every trip round adds a brighter layer, and the tail swells into a glittering choir that hangs in the air long after the note has stopped. Set the shifter to a fifth instead and you get more pipe organ than angels.
Brian Eno and Daniel Lanois are usually credited with building the effect in the studio in the 1980s out of separate harmonizers and reverb units. Today it ships as a mode in nearly every reverb plugin and guitar pedal, and remains the fastest way to make three chords sound like the soundtrack to a space documentary.