-A technique for detecting the pitches of a polyphonic signal of presented. The system utilises modified IIR comb filters, which are generated to ensure that n null (stop band notches) exists ut multiples of note fiequencies, and that a v e v j l a t pass band is present in the remain of the spectrum. Thw, the signal spectrum is not distorted after applying thejilters 60 the audio signal, which is the cme when using FIR combfilters. The presented approach improves upon an existing multi pitch detection model bared on an FIR comb filter framework,