Abstract: A digital audio signal processing technique in which the harmonic content of the output signal varies with the amplitude of an input signal. The preferred embodiment includes an analog to digital converter with sample and hold, a digital signal memory with playback control apparatus, timing circuits, a RAM look-up table to perform non-linear transformation and finally a digital to analog converter. The input signal, which can be an arbitrary audio signal or a digital signal representative of such a signal, is modified by a non-linear transformation means and outputted for reproduction in audible form or stored for subsequent processing.