Wallpaper Engine is what feeds it sound -- you can look within the "General" tab of the settings to see what audio device it grabs from.

Settings will be in the bottom right if you have it selected. If you need any more help, feel free to ask!

I can only get it to work through the mic and not through, for an example, spotify. Help?

Check the "General" tab in the Wallpaper Engine settings for an audio input selection!

I have the same issue. I've tried selecting all possible options in "Audio Input Device" but none seem to be picking up my music. Help would be much appreciated

Nothing I can do! :( That's a wallpaper engine / windows problem, unless you've tried other audio visualizers and they work just fine.

How do I make it appear on my background screen

At first it didn't work. I shut down program and then started it again and it works very good(I use spotify).

if you have the background pause "While another window is open" or playing sound, then it won't work. WHILE playing music.