The GMSN! Pure Sample and Hold is often paired with Noise source (GMSN! NOISE recommended, sold separately) to create randomly changing CV. This can then be patched into a VCO to create random sequences or, with more subtle use, to create "life-like" fluctuations, giving a more human feel to synthesised sounds.
The module has an internal clock, controlled by the Rate knob, an External Clock Input, Signal In and Signal Out jacks.