In a musical instrument having one or more tone generators in which a plurality of data words corresponding to the amplitudes of points defining the waveform of a musical tone are computed and transferred to a digital-to-analog converter to be converted into musical waveshapes, apparatus is provided for generating tones which are imitative of acoustic signals created by singing or humming. A new tone is obtained by singing into a microphone and actuating a switch. The output waveshapes are generated by implementing a Fourier transform algorithm using a set of harmonic coefficients determined by sampling and processing the signal produced by the microphone.