When an audio signal is allowed to overload the system conveying it, clipping is said to have occurred and severe distortion results. The ‘clipping point’ is reached when the audio system can no longer accommodate the signal amplitude –either because an analogue signal voltage nears or exceeds the circuitry’s power supply voltage, or because a digital sample amplitude exceeds the quantiser’s number range. In both cases, the result is that the signal peaks are ‘clipped’ because the system can’t support the peak excursions - a sinewave source signal becomes more like a squarewave. In an analogue system clipping produces strong harmonic distortion artefacts at frequencies above the fundamental. In a digital system those high frequency harmonics cause aliasing which results in anharmonic distortion where the distortion artefacts reproduce at frequencies below the source fundamental. This is why digital clipping sounds so unlike analogue clipping, and is far more unpleasant and less musical.