Spectral characteristics and efficient critical-band-associated group synthesis of piano tones

Abstract

The physics of piano sound production has been studied extensively, while little has been done to explore its spectral characteristics for efficient and perceptually accurate digital synthesis. Piano tones with a large variety of explicit performance parameters were recorded from a MIDI-controlled acoustic piano, and spectral modeling methods were used for the analysis. A number of features have been concluded: (1) relationship between harmonic structure and pitch for six levels of dynamic; (2) relationship between spectral envelope and dynamic for all pitches; (3) typical amplitude envelopes; (4) effects of the sustain and soft pedals; (5) inharmonicity characteristics; (6) noise characteristics. A multiple-wavetable synthesis algorithm implementing a group synthesis model was developed. Each harmonic group corresponds to one or more consecutive critical bands. Amplitude versus time envelopes of all harmonics within one group share a weighted-average shape with individual weight applied to each harmonic. With appropriate numbers of groups and characteristic noise, convincing results have been obtained for the entire range of pitches and dynamics. The synthesis algorithm has been implemented as a subroutine of an analysis/synthesis software package, as a Music 4C instrument, and as a real-time plug-in for a software sound server.