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Abstract

An audio apparatus extracts information of a musical performance from an acoustic signal having a frequency and an amplitude, which time-vary during the musical performance. In the audio apparatus, a filtering device has a plurality of filters which are set with different cutoff frequencies so as to pass different frequency ranges of the acoustic signal. A pitch detecting device is connected to the filtering device for processing the acoustic signal to detect therefrom a pitch. A controlling device operates according to the detected pitch fed back from the pitch detecting device for selecting one of the filters set with one of the different cutoff frequencies adapted to the pitch of the acoustic signal so that the pitch detecting device can detect the pitch based on the acoustic signal filtered by the selected filter. Further, the envelope detecting device has a plurality of envelope followers corresponding to the plurality of the filters. Each envelope follower processes the acoustic signal to extract therefrom an envelope representing a time-variation of the amplitude of the acoustic signal and containing an upward portion and a downward portion such that each envelope follower forms the downward portion by a given slope which matches the frequency range of the corresponding filter.

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First Claim