1. A method of operating an audio signal processing apparatus to process an audio signal, the method comprising: presenting a control interface to the user, the control interface including one or more control elements configured to accept a user input including user input that defines respective one or more values for at least some of a set of one or more blending parameters, the set of one or more blending parameters determining a user-defined dynamic equalization (DEQ) spectral profile based on a blending of two or more selected DEQ preset spectral profiles; determining from or accepting from the output of the control interface the user-defined dynamic equalization (DEQ) spectral profile based on a blending of two or more selected DEQ preset spectral profiles, the blending based on the set of one or more blending parameters, wherein each DEQ spectral profile comprises a set of measures for each band of a perceptually spaced set of frequency bands; and processing an audio signal according to the user-defined DEQ spectral profile to generate a processed audio signal, the processing including determining a spectral measure that is modified to dynamically adjust the time-varying spectrum of the audio signal to more closely match a time invariant spectral profile according to the user-defined DEQ spectral profile, wherein determining the time-varying spectrum comprises determining the specific loudness for the perceptually spaced set of frequency bands; wherein the processing includes perceptual domain dynamic equalization (PDEQ) to dynamically adjust the time-varying spectrum of the audio signal to more closely match the time invariant spectral profile according to the user-defined DEQ spectral profile, and wherein the blending is of a plurality of stored DEQ preset spectral profiles in the perceptually spaced set of frequency bands.