How I do mine:
I have a top level "Radio" entry. This could easily be a view nested under "Audio".
"Random Music", when selected, kicks off a Play Doctor playlist using the criteria last set under Play Doctor options "Set rules for files that can be included"
"Car Radio" uses the playlist group MC creates automatically when you use the buttons to save playlists. The beauty of these is that Play Doctor lists are saved as such, and behave as expected when when you kick them off.
"Online Radio" lists some direct radio streams that I have saved in my library.
To get the "Random Music" list to work, set theater view up like so:
Use the option to add an external program, and enter the following line in the "Program" field:
MC20.exe "/MCWS/v1/Playback/PlayDoctor"
For the "Car Radio" entry, use the option to add playlists, and choose the "Car Radio" group.
For online radio, I source the stream address, use
File > Open URL to get it playing, go to Playing Now, right click the stream entry and import. I then set a flag called Online Radio against it. I use a field called Type for this, but you can use any field that makes sense to you. You then exclude "Online Radio" from from your normal audio views which prevents the streams from popping up in randomly generated lists and other unwanted places.
Hope that helps a little, just ask if you need more.
-marko