Oh, you must have clicked on the button that turns the video output itself into audio and makes a bunch of terrible popping sounds.
It should pick up audio from whatever your default audio capture device is, so I take my mic and point it at a speaker and play music into Cathodemer that way. You can also set up internal routings using virtual audio cable programs if can figure out how to use them but I had trouble with that. But all you have to do is pick a parameter you want to modulate, right click it and select Arm to Audio Left or Right. Then go to the Extras tab and change the audio input gain, the base amount (which overrides the dedicated knob for whatever parameter you’re controlling), and the amount that the incoming audio will change that parameter. You can also set it to change based on the amplitude or frequency of the incoming audio, but so far I haven’t been able to get the frequency mode to do anything.