Classifying Pressure-Controlled Valves

• In physical modeling synthesis, the method used for simulating the reed typically depends on whether an additional upstream or downstream pressure causes the corresponding side of the valve to open or close further.

• The couplet $(\sigma_1, \sigma_2)$ may be used describe the upstream and downstream valve behaviour, respectively, where a value of +1 indicates an opening of the valve, and a value of -1 indicates a closing of the value, in response to a pressure increase.