This is just a last resort as an attempt. I reccomend clearing all the files from the bottom link (http://filesmelt.com/dl/Bass.DLL.zip) before doing this.
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\
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!
:Note: If you have previously installed and it has not worked then you can always copy these files into the right places.
http://filesmelt.com/dl/Bass.DLL.zip