Decomposition and modification of musical instrument sounds using a fractional delay allpass filter
Vesa Välimäki, Minna Ilmoniemi, Minna Huotilainen · Nordic Signal Processing Symposium · 2004
A method to decompose a harmonic musical signal into individual harmonic components and a noise component is proposed. The background noise can be extracted by subtracting from the original signal a delayed copy where the delay is the period length of the musical tone. A highly accurate approximation of the delay is imple- mented as a high-order allpass filter. Extracting individ- ual harmonic components involves the cancellation of one of the transmission zeros of the system by a pole. The method is easy and fast to use, and it allows accurate analysis and several useful modifications of musical tones. As an application example, three types of timbre modifications for recorded cello tones are demonstrated: change of the ratio of even and odd harmonic frequen- cies, of the spectral brightness, and of the amount of bowing noise. The resulting processed but natural- sounding signals are part of a test sound set used in a brain research task.