The Harmonic Tracking Equalizer (HTEq) is an apparatus for and method of carrying out harmonic tracking equalization processing of an electrical signal, and apparatuses for and methods of controlling such equalization processing of the signal to dynamically sense the time-varying spectrum of an input signal and closely match a user desired audio signal spectrum while preserving the original dynamic range of the signal. The harmonically (sub-harmonically) tracked equalization is according to a user specified spectral request specified by a control interface that allows a user to request an amount of equalization to be applied to the signal. This apparatus is intended to process audio signals; though, it has general application to waveforms of other source and higher frequency content.