The IEM Plug-in Suite was created by staff and students student of the Institute of Electronic Music and Acoustics in Graz. It is free and open source. Downloads and documentation can be found here https://plugins.iem.at/.
An in depth documentation of the IEM plugins features detailed information on installing and using the tools inside Reaper: https://plugins.iem.at/docs/.
The following pages include additional information on how to use the plugins with external software for control and processing, such as PD, SuperCollider and others.