Ring modulator   
A frequency/timbre altering device. 

Requires two inputs: A & B. outputs a set of frequencies which = the frequencies of A - the frequencies in B and the frequencies of A + the frequencies in B but not the original A or B signals.
 
one to six 
by Philip Glass		   one to six 
with dynamic ring modulation 26 seconds
 
In simple numeric terms:
if A is a sine wave of 440 Hz and B a 260 Hz sine wave then the ideal ring modulator will output only a 700 Hz sine + a 180 Hz sine.