The Smol Rat is a CV processor based on an accurate physical model of an RC network.
It started out life as a recreation of the portamento circuit in the Korg Micro-Preset M500. Once the project got underway however, it was realised that it could be extended to cover operation in the audio domain as well as for CV control signals. So now it can also be used as a 6dB/Oct LPF and HPF. The four main parameters are voltage-controllable and will track a 1V/oct input signal.