A technique is described for estimating the time-varying spectrum of an audio signal based on a conditional probability density function (PDF) of spectral coding vectors conditioned on pitch and loudness values. Using this PDF a time-varying output spectrum is generated as a function of time-varying pitch and loudness sequences arriving from an electronic music instrument controller or derived from an input audio signal. This output spectrum is converted to an output audio signal. The technique is used for both synthesizing and morphing audio signals.
