1. A data sonification system for representing a plurality of channels of numerical information via a plurality of corresponding discernable variations of timbre of at least one audio-frequency waveform, the audio-frequency waveform being perceivable by a user as an audio tone having a plurality of corresponding discernable timbre attributes, the system comprising: a plurality of audio-frequency waveform generators, each generating an associated audio-frequency waveform, wherein each audio-frequency waveform comprises a fixed audio-frequency and at least one adjustable timbre control parameter, each timbre control parameter having an associated adjustable value which can be discernibly varied within a timbre space occupied by the plurality of audio-frequency waveforms; and a mapping element for associating aspects of multidimensional numerical data with the at least one timbre control parameter of each of the audio-frequency waveforms from the plurality of audio-frequency waveforms, wherein for the plurality of audio-frequency waveforms the mapping element adjusts the value of the timbre control parameter responsive to values of the multidimensional numerical data, and wherein for the plurality of audio-frequency waveforms the timbre of the audio-frequency waveform carries information responsive to values of underlying data for presentation to a user.