Distortion in the form of unwanted frequencies corresponding to the sums and differences between various components of a complex waveform.
"dear cvcproductions: Recently I sent a 48 year-old lp of the eastman wind ensemble that you transferred to cd for me. I wanted to commend you on an excellent job. I am very pleased with the results. The sound is just wonderful considering the source you had to work with. I was also very pleased with the cd case and the transfer of the lp cover. ..."