A linear-interpolating sound generator based on the difference equations:
        x(n+1) = sin(im * y(n) + fb * x(n))
        y(n+1) = (a * y(n) + c) % 2pi
This uses a linear congruential function to drive the phase indexing of a sine wave. For im = 1, fb = 0, and a = 1 a normal sinewave results.
sclang code translation:
| freq | Iteration frequency in Hertz | 
| im | Index multiplier amount | 
| fb | Feedback amount | 
| a | Phase multiplier amount | 
| c | Phase increment amount | 
| xi | Initial value of x | 
| yi | Initial value of y |