Ring Modulation

Ring modulation multiplies two audio signals sample by sample, and the result contains only the sum and difference of their frequencies — the original inputs disappear from the output entirely. Because those sum and difference tones usually do not line up with the natural harmonic series, ring modulation produces clangorous, bell-like, and metallic timbres that are hard to achieve any other way. It is a classic tool for robotic voices, sci-fi effects, and inharmonic percussion. When the two frequencies are close together the effect is subtle and tremolo-like, but as they diverge the sound becomes increasingly strange and dissonant. Ring modulation is closely related to amplitude modulation and to FM, all of which generate new frequencies by combining oscillators.