A linear-interpolating sound generator based on the difference equations:
    x(n+1) = (x(n) + y(n+1)) % 2pi
    y(n+1) = (y(n) + k * sin(x(n))) % 2pi
The standard map is an area preserving map of a cylinder discovered by the plasma physicist Boris Chirikov.
sclang code translation:
| freq | Iteration frequency in Hertz | 
| k | Perturbation amount | 
| xi | Initial value of x | 
| yi | Initial value of y |