A method in accord with certain implementations involves, at an audio input, receiving a time domain audio signals; at one or more digital signal processors: converting the time domain audio signal to a frequency domain representation containing at least a fundamental frequency component, modifying the frequency domain representation to produce a modified frequency spectrum, converting the modified frequency spectrum to a modified time domain audio signal; and outputting the modified input signals as an output signal. This abstract is not to be considered limiting, since other embodiments may deviate from the features described in this abstract.