1. A music synthesizer, comprising: a sensor that generates an audio frequency sensor signal in response to direct stimulation of the sensor by a human user; and electronic circuitry for implementing a physical model, the electronic circuitry including: an excitation signal input port for continuously receiving the audio frequency sensor signal; a control signal port for receiving a control signal; and circuitry for generating an audio frequency output signal in accordance with the physical model, utilizing the audio frequency sensor signal received via the excitation signal port as an excitation signal for stimulating the physical model, and using the received control signal to set at least one parameter that controls the generation of the audio frequency output signal.