EchoLoop is a VST plugin (stereo) version of the legendary Echoplex Digital Pro, made by it’s inventor Matthias Grob. It is has not been developed for many years, but is still an amazing piece of software which hold its own with most modern alternatives. A Facebook group are now trying to restart the development. It is available as donationware from here.

Here is the Echoloop Manual.
A guide to using it with Ableton
The original Loop IV Guide covering many of it’s features
A playlist of Youtube videos

Michael Peters has made extensive use of the plugin, here are setups for 6 beats against 8 beats.

Cycle Looper

Freewheeling