The other day I was looking for a simple way to add radio to Mumble. I checked the main site, some "tutorials", but the only helpful information I found was some notes on a forum. After a bit of tinkering I got something working and wanted to share what it was.
So first off, you need a PC the radio is going to run on (aka a dedicated machine, a different laptop, whatever). Install the Mumble client on that machine.
Before launching and connecting to Mumble we need to make sure you have the proper audio-recording devices set up. Open your sound panel (Control Panel -> Sound or right-click the sound icon in task bar) and click the recording tab. In here you may or may not have "Stereo Mix" or "What You Hear". If you don't have either, then check out this tutorial to get it working.
A note on Stereo Mix and What U Hear: they work the same. On my older machine where the radio is hosted, I don't have an option to enable/install Stereo Mix. On my new laptop I only have Stereo Mix. Added a bit of confusion for me initially until I got it working.
Now that you have the proper sound devices, we need to mute everything. Go into the playback tab, double click on speakers (or where ever the green circle with check mark is), click on the levels tab and mute everything, except "Play Control". Next right-click on the volume icon and mute everything in there including "What U Hear" or "Stereo Mix" (if listed).
Next, connect to your Mumble server (this is all on the dedicated box if you got confused). I used a name like MyMumble.Radio or RadioBot (it can be whatever you like though). Now that you're connected, click on Configure and Settings. Under Audio Input select Stereo Mix or What U Hear as the device. And under audio output reduce the volume to 0%.
That's it! You can play music through any music player, through your browser (YouTube), Spotify, Last.fm/Pandora radio, etc. and it will stream through your Mumble RadioBot.
A couple notes before you begin. First, please turn your player/browser/whatever volume down VERY low to begin with. It can be extremely loud otherwise. Second, while this solution works great and is very simple, it can lag quite a bit if your connection is slow (my DSL can't really handle it).
Thanks for reading, and if you have any questions, please comment and I'll try and help out.
if TL;DR == TRUE then:
1. Install Mumble on dedicated box.
2. Enable/Install "Stereo Mix" or "What U Hear".
3. Mute all audio except the main device (speakers/Play Control) and music player/browser.
4. In Mumble, set audio input to Stereo Mix/What U Hear, set volume to 0% in audio output.
5. Play music and have jolly good time.