| 摘要 |
PURPOSE:To extract effectively and definitely only fundamental components from an input signal by proviing a variable characteristic filter which allows fundamental frequency components of the input signal including higher harmonics to pass through and by controlling this filter with the output of a fundamental wave detection circuit. CONSTITUTION:An input signal including a higher harmonic of a sound of a musical instrument performance is supplied to voltage control type variable characteristic filter 20 and fundamental wave detection circuit 22 via buffer 12. Circuit 22 is equipped with LPFs 23a, 23b... with their frequencies set higher in sequence, whose output signals are detected by signal detection circuits 24a, 24b . The sequence of the lowest-pass LPF 23a is supplied from circuit 24a to gate element 26a directly, but sequences of other LPFs 23b, 23c are inputted to gates 26b, 26c through AND circuits 25b, 25c , and 27, and inverters 28b, 28c and filter 20 is controlled by gate outputs. Consequently, the output signal of the lowest-pass filter LPF allowing the input signal to pass through is generated and signals of other filter sequences are inhibited, so that only fundamental wave components will be extracted. |
