The vibrations of the system are a function of the initial conditions, the forces applied by the performer, and the dynamics of the system. Examples include slowly vibrating strings, two dimensional surfaces obeying the wave equation, and a waterbed. We have simulated the string and surface models on a computer. Our waterbed model is purely conceptual. The ear cannot hear the low frequencies of the dynamic system.
Pitch control is completely separate from the dynamic system control.
Thus timbre and pitch are independent. This system can be looked upon as a dynamic wave table controlled by the performer. The psychophysical basis for Scanned Synthesis comes from our knowledge about human auditory perception and human motor control abilities. In the 1960's Risset showed that the spectra of interesting timbres must change with time. We observe that musically interesting change rates are less than about 15 hz which is also the rate humans can move their bodies.