As far as I can tell, this mode simply disables the audio inputs and emits a submarine sonar pulse sound at the clock rate. You can hear the raw sound with mix all the way down. Otherwise, turn the mix up and I’m pretty sure everything else works the same. It’s a little tricky because you can’t see the chroma color in this mode, and the low-pass and high-pass chromas don’t add much to this basic sound. But the distortions and wavefolding FX all seem to be there and do fun things.
Seems like a good way to make some ambient drone stuff without an audio input.