In this video, I use a pair of loop recorders to create a different type of feedback loop. This is meant to show a concept rather than be only a straight tutorial, though the video does show you one way to do it in Reaper using a plug-in called Mobius (link below).
I realized after recording this that there's probably a way to do this with a single instance of Mobius, since it can record to more than one internal "track", but I think this may make the concept more visibly clear anyway.
Links to plug-ins used in the video:
Atlantis Filter: http://jeremyevers.com/downloads/
Reaper and free versions of the included plug-ins can be downloaded from Cockos:
Feel free to ask any questions you may have in the comments.