This video, via DiscoverNoise, takes a look at the Synthesizers.com Q107 State Variable Filter.

The Q107 State Variable Filter is a 5U module that offers four outputs: Low Pass, Band Pass, Notch (Band Reject), and High Pass.

The video demos each of the outputs and the effect they’ve on the filtered audio, as well as all inputs (audio and cv). See the Synthesizers.com site for more info.