Protoverb is an experimental reverb based on the
idea of a "room simulator".
Most algorithmic reverbs try to avoid resonances or
model the reflections of sound from a rooms walls.
Protoverb does the opposite. It builds up as many
room resonances as possible, modeling the body of
air in the room. It therefore does not need to
modulate or colour the signal. The result is a very
natural sounding reverbration with some interesting
features: Long standing frequencies resonate louder,
as if the air takes some time to get excited.
Multiple instruments don't mash into a diffuse mud,
they stay distinct. If you play a short melody, the
room seems to repeat a ghost echo of that melody.
Those properties are indeed found in churches and
large halls, but they're rarely found in
conventional algorithmic reverbs.