The Ugly Face is a really interesting fuzz pedal that can do a lot more than the standard fuzz. Not only can it produce rip-your-head-off buzz saw tones, a synthesized octave down, and nasally tones, it also has an internal oscillator. When the level of incoming signal drops below the threshold level, the oscillator is triggered. The threshold level and oscillator frequency both have control knobs. It's really hard to describe this one, just take a listen.