Copycode

Copycode A system developed by CBS in 1987 to filter out a narrow band (“notch”) of musical frequencies in a master recording. The purpose was to give a cue to adecoder device installed by manufacturers of DAT recorders; the decoder’s response to the notch was toshut down the recorder. Thus unauthorized copying of a CD onto a DAT blank tape would be prevented. The notch itself was taken from the upper-middle range at 3.838 kHz; it was 112 Hz wide at the 3dB point and 90dB deep. Removing…