The μmod is a four quadrant multiplying modulator (aka ring mod) in 4 hp. it has the following features:

dedicated ac and dc inputs (all four can be used at the same time).
attenuators for x and y input groups.
polarity switches for x and y inputs (positive, negative or both).
a unique 'q' control which stands for "quadrant" which allows you to shift the multiplication into positive or negative quadrants.
very low leakage from x input (when q is in center).
changing the q value in fm adds the signal frequencies back into the sum+difference frequencies (typical output of a rigmod) which adds richness to the classic ringmod sound and allows for many variations of bell tones, chimes and mallet-type timbres.
it can be used as a linear vca.
great for waveshaping (especially two synced audio sources).
excellent for cv mangling (use the dc inputs and play with the rectifier switches).
connecting cv sources to the ac inputs results in interesting lag effects.