The Erica Synths Black Ring-Xfade is an extremely versatile module for sound shaping. It consists of two unconventional ringmodulators/waveshapers, a crossfader that works both for audio and CV and a VCA. Unlike conventional ringmodulator that works only with a signal present on both signal and carrier inputs, the Black Ring-Xfade passes through the signal without alteration, if no carrier is present, but low level signals on the carrier input result in unique waveshaping. Add the crossfader between two ringmodulators (or for an external signals) topped up with the VCA, and you have an amplitude modulation powerplant for your modular system.