A signal-processing model is proposed in which the phenomenon of 'aliasing' is invoked to explain certain phenomena in the perception of musical tones, for which a really satisfactory explanation has not hitherto been available. It is shown that this model offers a reason why the harmonic series appears to play such a central role in tone and pitch perception, and can throw light on 'virtual pitch', 'harmonic beats', etc. Some preliminary results from a computer simulation of the model are described which are consistent with empirical data on tone perception.