A non-interpolating sound generator based on the difference equations:
        x(n+1) = 1 - y(n) + |x(n)|
        y(n+1) = x(n)
The behavior of the system is only dependent on its initial conditions.
sclang code translation:
Reference: Devaney, R. L. "The Gingerbreadman." Algorithm 3, 15-16, Jan. 1992.
| freq | 
 Iteration frequency in Hertz  | 
| xi | 
 Initial value of x  | 
| yi | 
 Initial value of y  | 
| mul | |
| add |