MdspDuckDelay is a free delay and echo VST, Audio Unit plugin developed by Smart Electronix. Compatible OS(s): Windows 64b, macOS.
by mdsp of Smart Electronix
The output of mdspDuckDelay is compressed when the input signal reaches a threshold level. This allows you to use a lot of delay on a voice without losing too much intelligibility.
http://www.smartelectronix.com/