Electronical musical instrument with note frequency data setting circuit and interpolation circuit

Claim 1

An electronic musical instrument of the type that forms a musical waveform by calculating the waveform amplitude value at each sample point of the musical waveform through Fourier synthesis, comprising: a memory circuit for storing a plurality of sets of artibrary harmonic coefficients for use in the Fourier synthesis, each set of arbitrary harmonic coefficients including a series of arbitrary harmonic coefficients occupying different addresses in said memory circuit, said arbitrary harmonic coefficients in each set having a characteristic wave pattern of a musical waveform to be synthesized; a note frequency data setting circuit for setting a component ratio of a harmonic coefficient in accordance with the note frequency of a musical waveform to be synthesized, said note frequency data setting circuit selecting from and between the sets of arbitrary harmonic coefficients stored in said memory circuit; an address data generator for generatig readout addresses for reading out one set of the arbitrary harmonic coefficients from the memory circuit in accordance with the note frequency data of the musical waveform to be synthesized; an interpolation circuit for calculating actual harmonic coefficient data by starting at a starting address of the readout addresses from the address data generator, and by skipping by a selected skip value along the series of arbitrary harmonic coefficients in the readout addresses, the musical waveform to be synthesized having its characteristic wave pattern because of the selection of the set of arbitraryharmonic coefficients while having acual harmonic coefficients calculated by said interpolation circuit.