Tone signal generation device with interpolation of sample points

Abstract

A note clock generation circuit generates note clock pulses in correspondence to a note name of a tone to be generated. An octave rate data generation circuit generates rate data in correspondence to the octave range to which the tone to be generated belongs. By performing addition or subtraction of the rate data at the timing of generation of the note clock pulses, an address signal is generated. A tone generator generates a tone waveshape in the form of amplitude sampled values in response to an integer section of this address signal. An interpolation circuit performs interpolation between adjacent amplitude sampled values thus generated in response to a decimal section of the address signal. The rate of change of the decimal section of the address signal is changed in accordance with the tone range so that a finer interpolation is made as the tone range becomes lower. By this arrangement, decrease in an effective sampling frequency in the lower tone range can be prevented. The interpolation circuit receives the amplitude sampled values and the interpolation parameter (i.e., the decimal section of the address signal) respectively in a pitch synchronized state and performs the interpolation operation in the pitch synchronized state. The timing of the interpolation operation thereby is synchronized with the pitch of the generated tone so that inharmonic noise components are substantially removed.