This VST plugin adds echo and raises the pitch of an audio track to make it sound like it is inside an enclosed space such as a tunnel. Another VST completely transforms the original sound into a robotic or metallic tone while retaining the echo and pitch alterations of the first VST, allowing the two to work well in combination.

1. This VST adds an echo to the track and makes the
pitch higher, which could be used for the inside of
a tunnel or some other enclosed space.
This one completely alters the
previous sound making it sound
quite robotic/metallic.
It keeps the echo and pitch changes
from the previous VST too so they
work well together.