where x (in [-1..1] will be distorted and a is a distortion parameter that goes from 1 to infinity

The equation is valid for positive and negativ values.

If a is 1, it results in a slight distortion and with bigger a's the signal get's more funky.

A good thing about the shaper is that feeding it with bigger-than-one

values, doesn't create strange fx. The maximum this function will reach is

1.2 for a=1.

f(x,a) = x*(abs(x) + a)/(x^2 + (a-1)*abs(x) + 1)