A method for binding a computer program to an analog physical signature device to form an interactive system for controlling the use of the computer program, the method comprising the steps of providing instructions comprising the computer program, the instructions implementing an intended functionality, providing the analog physical signature device to which the computer program is to be bound, the analog physical signature device being operative, in response to an analog input, to transform the analog input into a consequent, dependent analog output, and replacing at least one code segment of the instructions representing a program expression, with an alternative code segment, the alternative code segment defining a predetermined digital input that is causally related to a predetermined analog input by means of the interactive system, the alternative code segment being operative, when encountered during execution of the instructions comprising the computer program, to cause the predetermined analog input to be communicated to the bound analog physical signature device by means of the interactive system, the bound analog physical signature device being operative to transform the predetermined analog input to a consequent, dependent analog output that is causally related to a consequent, dependent digital output by means of the interactive system, the alternative code segment being operative to perform program functionality dependent upon the predetermined digital input and the consequent, dependent digital output.