Tunable dispersion filter design for piano synthesis

The tunable dispersion filter is a new design approach presented in this letter to provide dispersion modeling for digital waveguide synthesis of musical instruments, which do not produce extremely inharmonic sounds, such as the piano. We propose to use a cascade of second-order allpass filters for modeling dispersion. The filter coefficients can be calculated by using simple formulae based on the Thiran allpass filter design, which is usually used for fractional delay approximation. Unlike the previous allpass filter approximations, this filter design is easily scalable to produce various inharmonicity values for a wide range of fundamental frequencies.