Below is a guide I had spare on my pc (Not sure if it overwrites existing files which might corrupt it.)
How to install Bass Module Application --.exe --
This is how to install the Bass Module for used on OCRP [exe Version] - It is exactly the same as the guide crap-head posted previously but it's simpler for those who don't understand folder placement and SVN's.
Download Link (http://filesmelt.com/dl/bass2.exe)
So after you have downloaded open the application on your desktop or wherever you downloaded it.
(http://speedcap.net/img/70676c353e6a3a0ee3703f1d742c248b/4a4e74a3.png)
Then simply check the destination folder is correct

It Should be c:\program files \steam\SteamApps\Steam User\garrysmod\ (Only first garrysmod folder, not second it's important)
Or for 64bit OS
c:\program files (x86)\steam\SteamApps\User\garrysmod\
Then Click Install

Now you are ready to listen to the radio on OCRP!
Hope this helped!