A type of amplitude modulation where the input levels of the carrier and modulation signals are balanced such that the original carrier and modulation frequencies disappear totally from the output, leaving only the sum and difference frequencies. The resulting frequencies are almost guaranteed to not be harmonically related, and ring modulation is often used to simulate the sounds of tuned percussion instruments that produce inharmonic frequency spectra, such as bells and chimes. Ring modulation can be a very difficult effect to control, but it can also produce timbres that are difficult to achieve by any other method of synthesis.