| 摘要 |
A pitch synchronizing signal snychronized with the pitch of a digital tone signal to be filtered is generated by a pitch synchronizing signal generation circuit. A digital filter circuit which receives the digital tone signal and imparts it with a desired tone color by subjecting it to a proper filter operation executes this filter operation with a sampling period synchronized with the pitch synchronizing signal. A moving formant thereby is realized which is suitable for control of a tone. A pitch synchronization output circuit for sampling and outputting the output of the digital filter circuit in accordance with the pitch synchronizing signal may be provided and this will prevent occurrence of a sampling noise. A switching circuit is provided for enabling switching order of the digital filter circuit between an even number and an odd number. By this switching of order, a desired filter characteristic can be realized with high fidelity. The filter coefficient may be used commonly for two orders positioned at symmetrical positions. Filter coefficients which do not undergo timewise change and those which undergo timewise change may be selectively supplied in separate channels.
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