RING-O can use the left and right
part of a stereo input as sources for the
modulation, or an input is ring-modulated by the
internal oscillator. Different waveforms, MIDI or
manual pitch control and continuous mixing offer
plenty of sound mangling options.
In addition the plugin features a
clean "math" form of ring modulation and a more
dirty "diode" emulation.
RING-O is free.